WebGrid - One of many useful ASP.NET Web Helpers.
Doing the HTML Yourself
In a previous chapter, you displayed database data by using razor code, and doing the HTML markup yourself:
Database Example
@{
var db = Database.Open("SmallBakery");
var selectQueryString = "SELECT * FROM Product ORDER BY Name";
}
<html>
<body>
<h1>Small Bakery Products</h1>
<table>
<tr>
<th>Id</th>
<th>Product</th>
<th>Description</th>
<th>Price</th>
</tr>
@foreach(var row in db.Query(selectQueryString))
{
<tr>
<td>@row.Id</td>
<td>@row.Name</td>
<td>@row.Description</td>
<td style="text-align:right">@row.Price</td>
</tr>
}
</table>
</body>
</html>
Using The WebGrid Helper
Using the WebGrid helper is an easier way to display data.
The WebGrid helper:
- Automatically sets up an HTML table to display data
- Supports different options for formatting
- Supports paging through data
- Supports Sorting by clicking on column headings
WebGrid Example
@{
var db = Database.Open("SmallBakery") ;
var selectQueryString = "SELECT * FROM Product ORDER BY Name";
var data = db.Query(selectQueryString);
var grid = new WebGrid(data);
}
<html>
<head>
<title>Displaying Data Using the WebGrid Helper</title>
</head>
<body>
<h1>Small Bakery Products</h1>
<div id="grid">
@grid.GetHtml()
</div>
</body>
</html>
WebGrid Object Reference
|
Helper
|
Description
|
|
WebGrid(data)
|
Creates a new WebGrid object using data from a query.
|
|
WebGrid.GetHtml()
|
Renders markup to display data in an HTML table.
|
|
WebGrid.Pager()
|
Renders a pager for the WebGrid object.
|
ASP.NET Web Pages - The Chart Helper
The Chart Helper - One of many useful ASP.NET Web Helpers.
The Chart Helper
In the previous chapters, you learned how to use an ASP.NET "Helper".
You learned how to display data in a grid using the "WebGrid Helper".
This chapter explains how to display data in graphical form, using the "Chart Helper".
The "Chart Helper" can create chart images of different types with many formatting options and labels. It can create standard charts like area charts, bar charts, column charts, line charts, and pie charts, along with more specialized charts like stock charts.
 
The data you display in a chart can be from an array, from a database, or from data in a file.
Chart From an Array
The example below shows the code needed to display a chart from an array of values:
Example
@{
var myChart = new Chart(width: 600, height: 400)
.AddTitle("Employees")
.AddSeries(chartType: "column",
xValue: new[] { "Peter", "Andrew", "Julie", "Mary", "Dave" },
yValues: new[] { "2", "6", "4", "5", "3" })
.Write();
}
- new Chart creates a new chart object and sets its width and height
- the AddTitle method specifies the chart title
- the AddSeries method adds data to the chart
- the chartType parameter defines the type of chart
- the xValue parameter defines x-axis names
- the yValues parameter defines the y-axis values
- the Write() method displays the chart
Chart From Database Data
You can run a database query and then use data from the results to create a chart:
Example
@{
var db = Database.Open("SmallBakery");
var dbdata = db.Query("SELECT Name, Price FROM Product");
var myChart = new Chart(width: 600, height: 400)
.AddTitle("Product Sales")
.DataBindTable(dataSource: dbdata, xField: "Name")
.Write();
}
- var db = Database.Open opens the database (and assigns the database object to the variable db)
- var dbdata = db.Query runs a database query and stores the result in dbdata
- new Chart creates a chart new object and sets its width and height
- the AddTitle method specifies the chart title
- the DataBindTable method binds the data source to the chart
- the Write() method displays the chart
An alternative to using the DataBindTable method is to use AddSeries (See previous example). DataBindTable is easier to use, but AddSeries is more flexible because you can specify the chart and data more explicitly:
Example
@{
var db = Database.Open("SmallBakery");
var dbdata = db.Query("SELECT Name, Price FROM Product");
var myChart = new Chart(width: 600, height: 400)
.AddTitle("Product Sales")
.AddSeries(chartType:"Pie",
xValue: dbdata, xField: "Name",
yValues: dbdata, yFields: "Price")
.Write();
}
Chart From XML Data
The third option for charting is to use an XML file as the data for the chart:
Example
@using System.Data;
@{
var dataSet = new DataSet();
dataSet.ReadXmlSchema(Server.MapPath("data.xsd"));
dataSet.ReadXml(Server.MapPath("data.xml"));
var dataView = new DataView(dataSet.Tables[0]);
var myChart = new Chart(width: 600, height: 400)
.AddTitle("Sales Per Employee")
.AddSeries("Default", chartType: "Pie",
xValue: dataView, xField: "Name",
yValues: dataView, yFields: "Sales")
.Write();}
}
Chart Object Reference
| Helper |
Description |
| Chart(width, height [, template] [, templatePath]) |
Initializes a chart. |
| Chart.AddLegend([title] [, name]) |
Adds a legend to a chart. |
Chart.AddSeries([name] [, chartType] [, chartArea]
[, axisLabel] [, legend] [, markerStep] [, xValue]
[, xField] [, yValues] [, yFields] [, options]) |
Adds a series of values to the chart. |
The WebMail Helper - One of many useful ASP.NET Web Helpers.
With the WebMail object you can easily send emails from a web page.
The WebMail Helper
The WebMail Helper makes it easy to send an email from a web application using SMTP (Simple Mail transfer Protocol).
Scenario: Email Support
To demonstrate the use of email, we will create an input page for support, let the user submit the page to another page, and send an email about the support problem.
First: Edit Your AppStart Page
If you have built the Demo application in this tutorial, you already have a page called _AppStart.cshtml with the following content:
_AppStart.cshtml
@{
WebSecurity.InitializeDatabaseConnection("Users", "UserProfile", "UserId", "Email", true);
}
To initiate the WebMail helper, add the the following WebMail properties to your AppStart page:
_AppStart.cshtml
@{
WebSecurity.InitializeDatabaseConnection("Users", "UserProfile", "UserId", "Email", true);
WebMail.SmtpServer = "smtp.example.com";
WebMail.SmtpPort = 25;
WebMail.EnableSsl = false;
WebMail.UserName = "[email protected]";
WebMail.Password = "password-goes-here";
WebMail.From = "[email protected]";
}
Properties explained:
SmtpServer: The name the SMTP server that will be used to send the emails.
SmtpPort: The port the server will use to send SMTP transactions (emails).
EnableSsl: True, if the server should use SSL (Secure Socket Layer) encryption.
UserName: The name of the SMTP email account used to send the email.
Password: The password of the SMTP email account.
From: The email to appear in the from address (often the same as UserName).
Second: Create an Email Input Page
Then create an input page, and name it Email_Input:
Email_Input.cshtml
<!DOCTYPE html>
<html>
<body>
<h1>Request for Assistance</h1>
<form method="post" action="EmailSend.cshtml">
<label>Username:</label>
<input type="text" name="customerEmail" />
<label>Details about the problem:</label>
<textarea name="customerRequest" cols="45" rows="4"></textarea>
<p><input type="submit" value="Submit" /></p>
</form>
</body>
</html>
The purpose of the input page is to collect information, then submit the data to a new page that can send the information as an email.
Third: Create An Email Send Page
Then create the page that will be used to send the email, and name it Email_Send:
Email_Send.cshtml
@{ // Read input
var customerEmail = Request["customerEmail"];
var customerRequest = Request["customerRequest"];
try
{
// Send email
WebMail.Send(to:"[email protected]", subject: "Help request from - " + customerEmail, body: customerRequest );
}
catch (Exception ex )
{
<text>@ex</text>
}
}
WebMail Object Reference - Properties
|
Properties
|
Description
|
|
SmtpServer
|
The name the SMTP server that will send the emails
|
|
SmtpPort
|
The port the server will use to send SMTP emails
|
|
EnableSsl
|
True, if the server should use SSL encryption
|
|
UserName
|
The name of the SMTP account used to send the email
|
|
Password
|
The password of the SMTP account
|
|
From
|
The email to appear in the from address
|
WebMail Object Reference - Methods
|
Method
|
Description
|
|
Send()
|
Sends an email message to an SMTP server for delivery
|
The Send() method has the following parameters:
|
Parameter
|
Type
|
Description
|
|
to
|
String
|
The Email recipients (separated by semicolon)
|
|
subject
|
String
|
The subject line
|
|
body
|
String
|
The body of the message
|
And the following optional parameters:
|
Parameter
|
Type
|
Description
|
|
from
|
String
|
The email of the sender
|
|
cc
|
String
|
The cc emails (separated by semicolon)
|
|
filesToAttach
|
Collection
|
Filenames
|
|
isBodyHtml
|
Boolean
|
True if the email body is in HTML
|
|
additionalHeaders
|
Collection
|
Additional headers
|
Technical Data
|
Name
|
Value
|
|
Class
|
System.Web.Helpers.WebMail
|
|
Namespace
|
System.Web.Helpers
|
|
Assembly
|
System.Web.Helpers.dll
|
Initializing the WebMail Helper
To use the WebMail helper, you need access to an SMTP server. SMTP is the "output" part of email. If you use a web host, you probably already know the name of the SMTP server. If you work in a corporate network, your IT department can give you the name. If you are working at home, you might be able to use your ordinary email provider.
In order to send an email you will need:
- The name of the SMTP server
- The port number (most often 25)
- An email user name
- An email password
In the root of your web, create a page (or edit the page ) named _AppStart.cshtml.
Put the following code inside the file:
_AppStart.cshtml
@{
WebMail.SmtpServer = "smtp.example.com";
WebMail.SmtpPort = 25;
WebMail.EnableSsl = false;
WebMail.UserName = "[email protected]";
WebMail.Password = "password";
WebMail.From = "[email protected]"
}
The code above will run each time the web site (application) starts. It feeds your WebMail Object with initial values.
Please substitute:
smtp.example.com with the name the SMTP server that will be used to send the emails.
25 with the port number the server will use to send SMTP transactions (emails).
false with true, if the server should use SSL (Secure Socket Layer) encryption.
[email protected] with the name of the SMTP email account used to send emails.
password with the password of the SMTP email account.
john@example with the email to appear in the from address.
You don't have to initiate the WebMail object in your AppStart file, but you must set these properties before you call the WebMail.Send() method.
Description
The WebSecurity Object provides security and authentication for ASP.NET Web Pages applications.
With the WebSecurity object you can create user accounts, login and logout users, reset or change passwords, and more.
WebSecurity Object Reference - Properties
WebSecurity Object Reference - Methods
Initializing the WebSecurity Database
You must create or initialize an WebSecurity database before you can use the WebSecurity object in your code.
In the root of your web, create a page (or edit the page ) named _AppStart.cshtml.
Put the following code inside the file:
_AppStart.cshtml
@{
WebSecurity.InitializeDatabaseConnection("Users", "UserProfile", "UserId", "Email", true);
}
The code above will run each time the web site (application) starts. It initializes the WebSecurity database.
"Users" is the name of the WebSecurity database (Users.sdf).
"UserProfile" is the name of the database table that contains the user profile information.
"UserId" is the name of the column that contains the user IDs (primary key).
"Email" is the name of the column that contains user names.
The last parameter true is a boolean value indicating that the user profile and membership tables should be created automatically if they don't exist, otherwise false.
Although true indicates automatic creation of the database tables, the database itself will not be created automatically. It must exist.
The WebSecurity Database
The UserProfile table contains one record for each user, with a user ID (primary key) and the user's name (email):
The Membership table will contain membership information about when the user was created and if (and when) the membership was confirmed.
Much like this (some columns are not shown):
|
User
Id
|
Create
Date
|
Confirmation
Token
|
Is
Confirmed
|
Last
Password
Failure
|
Password
|
Password
Change
|
|
1
|
12.04.2012 16:12:17
|
NULL
|
True
|
NULL
|
AFNQhWfy....
|
12.04.2012 16:12:17
|
Simple Membership Configuration
You might get errors using the WebSecurity object, if your site is not configured to use the ASP.NET Web Pages membership system SimpleMembership.
This can occur if a hosting provider's server is configured differently than your local server. To fix this, add the following element to the site's Web.config file:
<appSettings>
<add key="enableSimpleMembership" value="true" />
</appSettings>
1. Use the Latest Version of ASP.NET
Before you continue, make sure your hosting computer runs the latest version of ASP.NET (4.0 or 4.5).
2. Copy the Web Folders
Copy your website (all folders and content) from your development computer to an application folder on your remote hosting computer (server).
If your application contains data, don't copy the data (see point 4 below).
3. The DLL Files
Make sure the bin folder, on your remote hosting computer, contains the same dll files as on your development computer.
After copying the bin folder, it should contain files like this:
Microsoft.Web.Infrastructure.dll
NuGet.Core.dll
System.Web.Helpers.dll
System.Web.Razor.dll
System.Web.WebPages.Administration.dll
System.Web.WebPages.Deployment.dll
System.Web.WebPages.dll
System.Web.WebPages.Razor.dll
WebMatrix.Data.dll
WebMatrix.WebData
4. Copy Your Data
If your application contains data or a database. For instance an SQL Server Compact database (a .sdf file in App_Data folder), consider the following:
Do you want to publish your test data to the remote server?
Most likely not.
If you have test data on your development computer, it may overwrite production data on your remote hosting computer.
If you have to copy an SQL database (.sdf file), perhaps you should delete everything in the database, and then copy the empty .sdf file from your development computer to the server.
THAT'S IT. GOOD LUCK !
ASP.NET Web Pages - Examples in C# and VB
Learn ASP.NET Web Pages by C# and Visual Basic examples.
| Examples in C# |
Examples in VB |
Basic Web Pages
|
Basic Web Pages
|
Basic C#
|
Basic VB
|
Working with Databases
|
Working with Databases
|
Using the Chart Helper
|
Using the Chart Helper
|
ASP.NET Web Pages - Classes
ASP.NET Classes Reference
| Method |
Description |
| AsBool(), AsBool(true|false) |
Converts a string value to a Boolean value (true/false). Returns false or the specified value if the string does not represent true/false. |
| AsDateTime(), AsDateTime(value) |
Converts a string value to date/time. Returns DateTime. MinValue or the specified value if the string does not represent a date/time. |
| AsDecimal(), AsDecimal(value) |
Converts a string value to a decimal value. Returns 0.0 or the specified value if the string does not represent a decimal value. |
| AsFloat(), AsFloat(value) |
Converts a string value to a float. Returns 0.0 or the specified value if the string does not represent a decimal value. |
| AsInt(), AsInt(value) |
Converts a string value to an integer. Returns 0 or the specified value if the string does not represent an integer. |
| Href(path [, param1 [, param2]]) |
Creates a browser-compatible URL from a local file path, with optional additional path parts. |
| Html.Raw(value) |
Renders value as HTML markup instead of rendering it as HTML-encoded output. |
| IsBool(), IsDateTime(), IsDecimal(), IsFloat(), IsInt() |
Returns true if the value can be converted from a string to the specified type. |
| IsEmpty() |
Returns true if the object or variable has no value. |
| IsPost |
Returns true if the request is a POST. (Initial requests are usually a GET.) |
| Layout |
Specifies the path of a layout page to apply to this page. |
| PageData[key], PageData[index], Page |
Contains data shared between the page, layout pages, and partial pages in the current request. You can use the dynamic Page property to access the same data, as in the following example: |
| RenderBody() |
(Layout pages) Renders the content of a content page that is not in any named sections. |
RenderPage(path, values)
RenderPage(path[, param1 [, param2]]) |
Renders a content page using the specified path and optional extra data. You can get the values of the extra parameters from PageData by position (example 1) or key (example 2). |
| RenderSection(sectionName [, required = true|false]) |
(Layout pages) Renders a content section that has a name. Set required to false to make a section optional. |
| Request.Cookies[key] |
Gets or sets the value of an HTTP cookie. |
| Request.Files[key] |
Gets the files that were uploaded in the current request. |
| Request.Form[key] |
Gets data that was posted in a form (as strings). Request[key] checks both the Request.Form and the Request.QueryString collections. |
| Request.QueryString[key] |
Gets data that was specified in the URL query string. Request[key] checks both the Request.Form and the Request.QueryString collections. |
Request.Unvalidated(key)
Request.Unvalidated().QueryString|Form|Cookies|Headers[key] |
Selectively disables request validation for a form element, query-string value, cookie, or header value. Request validation is enabled by default and prevents users from posting markup or other potentially dangerous content. |
| Response.AddHeader(name, value) |
Adds an HTTP server header to the response. |
| Response.OutputCache(seconds [, sliding] [, varyByParams]) |
Caches the page output for a specified time. Optionally set sliding to reset the timeout on each page access and varyByParams to cache different versions of the page for each different query string in the page request. |
| Response.Redirect(path) |
Redirects the browser request to a new location. |
| Response.SetStatus(httpStatusCode) |
Sets the HTTP status code sent to the browser. |
| Response.WriteBinary(data [, mimetype]) |
Writes the contents of data to the response with an optional MIME type. |
| Response.WriteFile(file) |
Writes the contents of a file to the response. |
| @section(sectionName) { content } |
(Layout pages) Defines a content section that has a name. |
| Server.HtmlDecode(htmlText) |
Decodes a string that is HTML encoded. |
| Server.HtmlEncode(text) |
Encodes a string for rendering in HTML markup. |
| Server.MapPath(virtualPath) |
Returns the server physical path for the specified virtual path. |
| Server.UrlDecode(urlText) |
Decodes text from a URL. |
| Server.UrlEncode(text) |
Encodes text to put in a URL. |
| Session[key] |
Gets or sets a value that exists until the user closes the browser. |
| ToString() |
Displays a string representation of the object's value. |
| UrlData[index] |
Gets additional data from the URL (for example, /MyPage/ExtraData). |
Razor is not a programming language. It's a server side markup language.
What is Razor?
Razor is a markup syntax that lets you embed server-based code (Visual Basic and C#) into web pages.
Server-based code can create dynamic web content on the fly, while a web page is written to the browser. When a web page is called, the server executes the server-based code inside the page before it returns the page to the browser. By running on the server, the code can perform complex tasks, like accessing databases.
Razor is based on ASP.NET, and designed for creating web applications. It has the power of traditional ASP.NET markup, but it is easier to use, and easier to learn.
Razor Syntax
Razor uses a syntax very similar to PHP and Classic ASP.
Razor:
<ul>
@for (int i = 0; i < 10; i++) {
<li>@i</li>
}
</ul>
PHP:
<ul>
<?php
for ($i = 0; $i < 10; $i++) {
echo("<li>$i</li>");
}
?>
</ul>
Classic ASP:
<ul>
<%for i = 0 to 10%>
<li><%=i%></li>
<%next%>
</ul>
Razor Helpers
ASP.NET helpers are components that can be accessed by single lines of Razor code.
You can build your own helpers using Razor syntax, or use built-in ASP.NET helpers.
Below is a short description of some useful Razor helpers:
- Web Grid
- Web Graphics
- Google Analytics
- Facebook Integration
- Twitter Integration
- Sending Email
- Validation
Razor Programming Languages
Razor supports both C# (C sharp) and VB (Visual Basic).
Razor supports both C# (C sharp) and VB (Visual Basic).
Main Razor Syntax Rules for C#
- Razor code blocks are enclosed in @{ ... }
- Inline expressions (variables and functions) start with @
- Code statements end with semicolon
- Variables are declared with the var keyword
- Strings are enclosed with quotation marks
- C# code is case sensitive
- C# files have the extension .cshtml
C# Example
<!-- Single statement block -->
@{ var myMessage = "Hello World"; }
<!-- Inline expression or variable -->
<p>The value of myMessage is: @myMessage</p>
<!-- Multi-statement block -->
@{
var greeting = "Welcome to our site!";
var weekDay = DateTime.Now.DayOfWeek;
var greetingMessage = greeting + " Here in Huston it is: " + weekDay;
}
<p>The greeting is: @greetingMessage</p>
Main Razor Syntax Rules for VB
- Razor code blocks are enclosed in @Code ... End Code
- Inline expressions (variables and functions) start with @
- Variables are declared with the Dim keyword
- Strings are enclosed with quotation marks
- VB code is not case sensitive
- VB files have the extension .vbhtml
Example
<!-- Single statement block -->
@Code dim myMessage = "Hello World" End Code
<!-- Inline expression or variable -->
<p>The value of myMessage is: @myMessage</p>
<!-- Multi-statement block -->
@Code
dim greeting = "Welcome to our site!"
dim weekDay = DateTime.Now.DayOfWeek
dim greetingMessage = greeting & " Here in Huston it is: " & weekDay
End Code
<p>The greeting is: @greetingMessage</p>
How Does it Work?
Razor is a simple programming syntax for embedding server code in web pages.
Razor syntax is based on the ASP.NET framework, the part of the Microsoft.NET Framework that's specifically designed for creating web applications.
The Razor syntax gives you all the power of ASP.NET, but is using a simplified syntax that's easier to learn if you're a beginner, and makes you more productive if you're an expert.
Razor web pages can be described as HTML pages with two kinds of content: HTML content and Razor code.
When the server reads the page, it runs the Razor code first, before it sends the HTML page to the browser. The code that is executed on the server can perform tasks that cannot be done in the browser, for example accessing a server database. Server code can create dynamic HTML content on the fly, before it is sent to the browser. Seen from the browser, the HTML generated by server code is no different than static HTML content.
ASP.NET web pages with Razor syntax have the special file extension cshtml (Razor using C#) or vbhtml (Razor using VB).
Working With Objects
Server coding often involves objects.
The "DateTime" object is a typical built-in ASP.NET object, but objects can also be self-defined, a web page, a text box, a file, a database record, etc.
Objects may have methods they can perform. A database record might have a "Save" method, an image object might have a "Rotate" method, an email object might have a "Send" method, and so on.
Objects also have properties that describe their characteristics. A database record might have a FirstName and a LastName property (among others).
The ASP.NET DateTime object has a Now property (written as DateTime.Now), and the Now property has a Day property (written as DateTime.Now.Day). The example below shows how to access some properties of the DateTime object:
Example
<table border="1">
<tr>
<th width="100px">Name</th>
<td width="100px">Value</td>
</tr>
<tr>
<td>Day</td><td>@DateTime.Now.Day</td>
</tr>
<tr>
<td>Hour</td><td>@DateTime.Now.Hour</td>
</tr>
<tr>
<td>Minute</td><td>@DateTime.Now.Minute</td>
</tr>
<tr>
<td>Second</td><td>@DateTime.Now.Second</td>
</tr>
</td>
</table>
If and Else Conditions
An important feature of dynamic web pages is that you can determine what to do based on conditions.
The common way to do this is with the if ... else statements:
Example
@{
var txt = "";
if(DateTime.Now.Hour > 12)
{txt = "Good Evening";}
else
{txt = "Good Morning";}
}
<html>
<body>
<p>The message is @txt</p>
</body>
</html>
Reading User Input
Another important feature of dynamic web pages is that you can read user input.
Input is read by the Request[] function, and posting (input) is tested by the IsPost condition:
Example
@{
var totalMessage = "";
if(IsPost)
{
var num1 = Request["text1"];
var num2 = Request["text2"];
var total = num1.AsInt() + num2.AsInt();
totalMessage = "Total = " + total;
}
}
<html>
<body style="background-color: beige; font-family: Verdana, Arial;">
<form action="" method="post">
<p><label for="text1">First Number:</label><br>
<input type="text" name="text1" /></p>
<p><label for="text2">Second Number:</label><br>
<input type="text" name="text2" /></p>
<p><input type="submit" value=" Add " /></p>
</form>
<p>@totalMessage</p>
</body>
</html>
Variables are named entities used to store data.
Variables
Variables are used to store data.
The name of a variable must begin with an alphabetic character and cannot contain whitespace or reserved characters.
A variable can be of a specific type, indicating the kind of data it stores. String variables store string values ("Welcome to W3Schools"), integer variables store number values (103), date variables store date values, etc.
Variables are declared using the var keyword, or by using the type (if you want to declare the type), but ASP.NET can usually determine data types automatically.
Examples
// Using the var keyword:
var greeting = "Welcome to W3Schools";
var counter = 103;
var today = DateTime.Today;
// Using data types:
string greeting = "Welcome to W3Schools";
int counter = 103;
DateTime today = DateTime.Today;
Data Types
Below is a list of common data types:
|
Type
|
Description
|
Examples
|
|
int
|
Integer (whole numbers)
|
103, 12, 5168
|
|
float
|
Floating-point number
|
3.14, 3.4e38
|
|
decimal
|
Decimal number (higher precision)
|
1037.196543
|
|
bool
|
Boolean
|
true, false
|
|
string
|
String
|
"Hello W3Schools", "John"
|
Operators
An operator tells ASP.NET what kind of command to perform in an expression.
The C# language supports many operators. Below is a list of common operators:
|
Operator
|
Description
|
Example
|
|
=
|
Assigns a value to a variable.
|
i=6
|
|
+
-
*
/
|
Adds a value or variable.
Subtracts a value or variable.
Multiplies a value or variable.
Divides a value or variable.
|
i=5+5
i=5-5
i=5*5
i=5/5
|
|
+=
-=
|
Increments a variable.
Decrements a variable.
|
i += 1
i -= 1
|
|
==
|
Equality. Returns true if values are equal.
|
if (i==10)
|
|
!=
|
Inequality. Returns true if values are not equal.
|
if (i!=10)
|
|
<
>
<=
>=
|
Less than.
Greater than.
Less than or equal.
Greater than or equal.
|
if (i<10)
if (i>10)
if (i<=10)
if (i>=10)
|
|
+
|
Adding strings (concatenation).
|
"w3" + "schools"
|
|
.
|
Dot. Separate objects and methods.
|
DateTime.Hour
|
|
()
|
Parenthesis. Groups values.
|
(i+5)
|
|
()
|
Parenthesis. Passes parameters.
|
x=Add(i,5)
|
|
[]
|
Brackets. Accesses values in arrays or collections.
|
name[3]
|
|
!
|
Not. Reverses true or false.
|
if (!ready)
|
|
&&
||
|
Logical AND.
Logical OR.
|
if (ready && clear)
if (ready || clear)
|
Converting Data Types
Converting from one data type to another is sometimes useful.
The most common example is to convert string input to another type, such as an integer or a date.
As a rule, user input comes as strings, even if the user entered a number. Therefore, numeric input values must be converted to numbers before they can be used in calculations.
Below is a list of common conversion methods:
|
Method
|
Description
|
Example
|
|
AsInt()
IsInt()
|
Converts a string to an integer.
|
if (myString.IsInt())
{myInt=myString.AsInt();}
|
|
AsFloat()
IsFloat()
|
Converts a string to a floating-point number.
|
if (myString.IsFloat())
{myFloat=myString.AsFloat();}
|
|
AsDecimal()
IsDecimal()
|
Converts a string to a decimal number.
|
if (myString.IsDecimal())
{myDec=myString.AsDecimal();}
|
|
AsDateTime()
IsDateTime()
|
Converts a string to an ASP.NET DateTime type.
|
myString="10/10/2012";
myDate=myString.AsDateTime();
|
|
AsBool()
IsBool()
|
Converts a string to a Boolean.
|
myString="True";
myBool=myString.AsBool();
|
|
ToString()
|
Converts any data type to a string.
|
myInt=1234;
myString=myInt.ToString();
|
Statements can be executed repeatedly in loops.
For Loops
If you need to run the same statements repeatedly, you can program a loop.
If you know how many times you want to loop, you can use a for loop. This kind of loop is especially useful for counting up or counting down:
Example
<html>
<body>
@for(var i = 10; i < 21; i++)
{<p>Line @i</p>}
</body>
</html>
For Each Loops
If you work with a collection or an array, you often use a for each loop.
A collection is a group of similar objects, and the for each loop lets you carry out a task on each item. The for each loop walks through a collection until it is finished.
The example below walks through the ASP.NET Request.ServerVariables collection.
Example
<html>
<body>
<ul>
@foreach (var x in Request.ServerVariables)
{<li>@x</li>}
</ul>
</body>
</html>
While Loops
The while loop is a general purpose loop.
A while loop begins with the while keyword, followed by parentheses, where you specify how long the loop continues, then a block to repeat.
While loops typically add to, or subtract from, a variable used for counting.
In the example below, the += operator adds 1 to the variable i, each time the loop runs.
Example
<html>
<body>
@{
var i = 0;
while (i < 5)
{
i += 1;
<p>Line @i</p>
}
}
</body>
</html>
Arrays
An array is useful when you want to store similar variables but don't want to create a separate variable for each of them:
Example
@{
string[] members = {"Jani", "Hege", "Kai", "Jim"};
int i = Array.IndexOf(members, "Kai")+1;
int len = members.Length;
string x = members[2-1];
}
<html>
<body>
<h3>Members</h3>
@foreach (var person in members)
{
<p>@person</p>
}
<p>The number of names in Members are @len</p>
<p>The person at position 2 is @x</p>
<p>Kai is now in position @i</p>
</body>
</html>
Programming Logic: Execute code based on conditions.
The If Condition
C# lets you execute code based on conditions.
To test a condition you use an if statement. The if statement returns true or false, based on your test:
- The if statement starts a code block
- The condition is written inside parenthesis
- The code inside the braces is executed if the test is true
Example
@{var price=50;}
<html>
<body>
@if (price>30)
{
<p>The price is too high.</p>
}
</body>
</html>
The Else Condition
An if statement can include an else condition.
The else condition defines the code to be executed if the condition is false.
Example
@{var price=20;}
<html>
<body>
@if (price>30)
{
<p>The price is too high.</p>
}
else
{
<p>The price is OK.</p>
}
</body>
</html>
Note: In the example above, if the first condition is true, it will be executed. The else condition covers "everything else".
The Else If Condition
Multiple conditions can be tested with an else if condition:
Example
@{var price=25;}
<html>
<body>
@if (price>=30)
{
<p>The price is high.</p>
}
else if (price>20 && price<30)
{
<p>The price is OK.</p>
}
else
{
<p>The price is low.</p>
}
</body>
</html>
In the example above, if the first condition is true, it will be executed.
If not, then if the next condition is true, this condition will be executed.
You can have any number of else if conditions.
If none of the if and else if conditions are true, the last else block (without a condition) covers "everything else".
Switch Conditions
A switch block can be used to test a number of individual conditions:
Example
@{
var weekday=DateTime.Now.DayOfWeek;
var day=weekday.ToString();
var message="";
}
<html>
<body>
@switch(day)
{
case "Monday":
message="This is the first weekday.";
break;
case "Thursday":
message="Only one day before weekend.";
break;
case "Friday":
message="Tomorrow is weekend!";
break;
default:
message="Today is " + day;
break;
}
<p>@message</p>
</body>
</html>
The test value (day) is in parentheses. Each individual test condition has a case value that ends with a colon, and any number of code lines ending with a break statement. If the test value matches the case value, the code lines are executed.
A switch block can have a default case (default:) for "everything else" that runs if none of the cases are true.
Variables are named entities used to store data.
Variables
Variables are used to store data.
The name of a variable must begin with an alphabetic character and cannot contain whitespace or reserved characters.
A variable can be of a specific type, indicating the kind of data it stores. String variables store string values ("Welcome to W3Schools"), integer variables store number values (103), date variables store date values, etc.
Variables are declared using the Dim keyword, or by using the type (if you want to declare the type), but ASP.NET can usually determine data types automatically.
Examples
// Using the Dim keyword:
Dim greeting = "Welcome to W3Schools"
Dim counter = 103
Dim today = DateTime.Today
// Using data types:
Dim greeting As String = "Welcome to W3Schools"
Dim counter As Integer = 103
Dim today As DateTime = DateTime.Today
Data Types
Below is a list of common data types:
|
Type
|
Description
|
Examples
|
|
integer
|
Integer (whole numbers)
|
103, 12, 5168
|
|
double
|
64 bit floating-point number
|
3.14, 3.4e38
|
|
decimal
|
Decimal number (higher precision)
|
1037.196543
|
|
boolean
|
Boolean
|
true, false
|
|
string
|
String
|
"Hello W3Schools", "John"
|
Operators
An operator tells ASP.NET what kind of command to perform in an expression.
The VB language supports many operators. Below is a list of common operators:
|
Operator
|
Description
|
Example
|
|
=
|
Assigns a value to a variable.
|
i=6
|
|
+
-
*
/
|
Adds a value or variable.
Subtracts a value or variable.
Multiplies a value or variable.
Divides a value or variable.
|
i=5+5
i=5-5
i=5*5
i=5/5
|
|
+=
-=
|
Increments a variable.
Decrements a variable.
|
i += 1
i -= 1
|
|
=
|
Equality. Returns true if values are equal.
|
if i=10
|
|
<>
|
Inequality. Returns true if values are not equal.
|
if <>10
|
|
<
>
<=
>=
|
Less than.
Greater than.
Less than or equal.
Greater than or equal.
|
if i<10
if i>10
if i<=10
if i>=10
|
|
&
|
Adding strings (concatenation).
|
"w3" & "schools"
|
|
.
|
Dot. Separate objects and methods.
|
DateTime.Hour
|
|
()
|
Parenthesis. Groups values.
|
(i+5)
|
|
()
|
Parenthesis. Passes parameters.
|
x=Add(i,5)
|
|
()
|
Parenthesis. Accesses values in arrays or collections.
|
name(3)
|
|
Not
|
Not. Reverses true or false.
|
if Not ready
|
|
And
OR
|
Logical AND.
Logical OR.
|
if ready And clear
if ready Or clear
|
|
AndAlso
orElse
|
Extended Logical AND.
Extended Logical OR.
|
if ready AndAlso clear
if ready OrElse clear
|
Converting Data Types
Converting from one data type to another is sometimes useful.
The most common example is to convert string input to another type, such as an integer or a date.
As a rule, user input comes as strings, even if the user entered a number. Therefore, numeric input values must be converted to numbers before they can be used in calculations.
Below is a list of common conversion methods:
|
Method
|
Decryptions
|
Example
|
|
AsInt()
IsInt()
|
Converts a string to an integer.
|
if myString.IsInt() then
myInt=myString.AsInt()
end if
|
|
AsFloat()
IsFloat()
|
Converts a string to a floating-point number.
|
if myString.IsFloat() then
myFloat=myString.AsFloat()
end if
|
|
AsDecimal()
IsDecimal()
|
Converts a string to a decimal number.
|
if myString.IsDecimal() then
myDec=myString.AsDecimal()
end if
|
|
AsDateTime()
IsDateTime()
|
Converts a string to an ASP.NET DateTime type.
|
myString="10/10/2012"
myDate=myString.AsDateTime()
|
|
AsBool()
IsBool()
|
Converts a string to a Boolean.
|
myString="True"
myBool=myString.AsBool()
|
|
ToString()
|
Converts any data type to a string.
|
myInt=1234
myString=myInt.ToString()
|
Statements can be executed repeatedly in loops.
For Loops
If you need to run the same statements repeatedly, you can program a loop.
If you know how many times you want to loop, you can use a for loop. This kind of loop is especially useful for counting up or counting down:
Example
<html>
<body>
@For i=10 To 21
@<p>Line #@i</p>
Next i
</body>
</html>
For Each Loops
If you work with a collection or an array, you often use a for each loop.
A collection is a group of similar objects, and the for each loop lets you carry out a task on each item. The for each loop walks through a collection until it is finished.
The example below walks through the ASP.NET Request.ServerVariables collection.
Example
<html>
<body>
<ul>
@For Each x In Request.ServerVariables
@<li>@x</li>
Next x
</ul>
</body>
</html>
While Loops
The while loop is a general purpose loop.
A while loop begins with the while keyword, followed by parentheses, where you specify how long the loop continues, then a block to repeat.
While loops typically add to, or subtract from, a variable used for counting.
In the example below, the += operator adds 1 to the variable i, each time the loop runs.
Example
<html>
<body>
@Code
Dim i=0
Do While i<5
i += 1
@<p>Line #@i</p>
Loop
End Code
</body>
</html>
Arrays
An array is useful when you want to store similar variables but don't want to create a separate variable for each of them:
Example
@Code
Dim members As String()={"Jani","Hege","Kai","Jim"}
i=Array.IndexOf(members,"Kai")+1
len=members.Length
x=members(2-1)
end Code
<html>
<body>
<h3>Members</h3>
@For Each person In members
@<p>@person</p>
Next person
<p>The number of names in Members are @len</p>
<p>The person at position 2 is @x</p>
<p>Kai is now in position @i</p>
</body>
</html>
Programming Logic: Execute code based on conditions.
The If Condition
VB lets you execute code based on conditions.
To test a condition you use the if statement. The if statement returns true or false, based on your test:
- The if statement starts a code block
- The condition is written between if and then
- The code between if ... then and end if is executed if the test is true
Example
@Code
Dim price=50
End Code
<html>
<body>
@If price>30 Then
@<p>The price is too high.</p>
End If
</body>
</html>
The Else Condition
An if statement can include an else condition.
The else condition defines the code to be executed if the condition is false.
Example
@Code
Dim price=20
End Code
<html>
<body>
@if price>30 then
@<p>The price is too high.</p>
Else
@<p>The price is OK.</p>
End If
</body>
</html>
Note: In the example above, if the first condition is true, it will be executed. The else condition covers "everything else".
The ElseIf Condition
Multiple conditions can be tested with an else if condition:
Example
@Code
Dim price=25
End Code
<html>
<body>
@If price>=30 Then
@<p>The price is high.</p>
ElseIf price>20 And price<30 then
@<p>The price is OK.</p>
Else
@<p>The price is low.</p>
End If
</body>
</html>
In the example above, if the first condition is true, it will be executed.
If not, then if the next condition is true, this condition will be executed.
You can have any number of else if conditions.
If none of the if or else if conditions are true, the last else block (without a condition) covers "everything else".
Select Conditions
A select block can be used to test a number of individual conditions:
Example
@Code
Dim weekday=DateTime.Now.DayOfWeek
Dim day=weekday.ToString()
Dim message=""
End Code
<html>
<body>
@Select Case day
Case "Monday"
message="This is the first weekday."
Case "Thursday"
message="Only one day before weekend."
Case "Friday"
message="Tomorrow is weekend!"
Case Else
message="Today is " & day
End Select
<p>@message</p>
</body>
</html>
"Select Case" is followed by the test value (day). Each individual test condition has a case value, and any number of code lines. If the test value matches the case value, the code lines are executed.
A select block can have a default case (Case Else) for "everything else" that runs if none of the other cases are true.
ASP is an old (but still powerful) tool for making dynamic Web pages.
ASP is a technology (much like PHP) for executing scripts on a web server.
In this tutorial you will learn all you need to know about ASP.
Easy Learning with "Show Example"
This ASP tutorial contains hundreds of examples.
Our "Show Example" tool makes it easy to learn ASP, because it shows ASP code with parallel HTML output.
Example
<!DOCTYPE html>
<html>
<body>
<%
response.write("My first ASP script!")
%>
</body>
</html>
Click on the "Show Example" button to see how it works!
What is ASP?
- ASP stands for Active Server Pages
- ASP is a Microsoft Technology
- ASP is a program that runs inside a web server
What is an ASP File?
- An ASP file has the file extension ".asp"
- An ASP file is just the same as an HTML file
- An ASP file can contain server scripts in addition to HTML
- Server scripts in an ASP file are executed on the server
What can ASP do for you?
- Edit, change, add content, or customize any web page
- Respond to user queries or data submitted from HTML forms
- Access databases or other server data and return results to a browser
- Provide web security since ASP code cannot be viewed in a browser
- Offer simplicity and speed
How Does it Work?
When a browser requests a normal HTML file, the server just returns the file.
When a browser requests an ASP file, the server passes the request to the ASP engine which reads the ASP file and executes the server scripts in the file.
Finally the ASP file is returned to the browser as plain HTML.
ASP References
At W3Schools you will find complete ASP references about built-in objects and components, and their properties and methods.
ASP Examples
Learn by 100 examples! Because ASP scripts are executed on the server, you can not view ASP code in a browser, you will only see the output from ASP which is plain HTML. At W3Schools every example displays the hidden ASP code. This will make it easier for you to understand how it works.
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All our examples shows the ASP code in red.
This makes it easier for you to understand how ASP works.
ASP Uses VBScript
The default scripting language in ASP is VBScript.
A scripting language is a lightweight programming language.
VBScript is a light version of Microsoft's Visual Basic.
ASP Files
ASP files can be ordinary HTML files. In addition, ASP files can also contain server scripts.
Scripts surrounded by <% and %> are executed on the server.
The Response.Write() method is used by ASP to write output to HTML.
The following example writes "Hello World" into HTML:
Example
<!DOCTYPE html>
<html>
<body>
<%
Response.Write("Hello World!")
%>
</body>
</html>
VBScript is case insensitive. Response.Write() can be written as response.write().
Using JavaScript in ASP
To set JavaScript as the scripting language for a web page you must insert a language specification at the top of the page:
Example
<%@ language="javascript"%>
<!DOCTYPE html>
<html>
<body>
<%
Response.Write("Hello World!")
%>
</body>
</html>
This tutorial uses the VBScript scripting language.
More Examples
There is an easy shortcut to Response.Write(). You can use an equal sign (=) instead.
The following example also writes "Hello World" into HTML:
Example
<!DOCTYPE html>
<html>
<body>
<%
="Hello World!"
%>
</body>
</html>
HTML tags can be a part of the output:
Example
<!DOCTYPE html>
<html>
<body>
<%
Response.Write("<h2>You can use HTML tags to format the text!</h2>")
%>
</body>
</html>
HTML attributes can be a part of the output:
Example
<!DOCTYPE html>
<html>
<body>
<%
Response.Write("<p style='color:#0000ff'>This text is styled.</p>")
%>
</body>
</html>
VBScript Examples
This tutorial contains a lot of VBScript examples.
VBScript Reference
This tutorial has complete VBScript reference.
ASP Variables
Variables are "containers" for storing information.
More Examples
This example demonstrates how to declare a variable, assign a value to it, and use the value in a text.
Arrays are used to store a series of related data items. This example demonstrates how to create an array that stores names.
How to loop through the six headings in HTML.
This example will display a different message to the user depending on the time on the server.
This example is the same as the one above, but the syntax is different.
How to create a variable, assign a value to it, and then change the value of it.
How to insert a variable value in a text.
Do You Remember Algebra from School?
Do you remember algebra from school? x=5, y=6, z=x+y
Do you remember that a letter (like x) could be used to hold a value (like 5), and that you could use the information above to calculate the value of z to be 11?
These letters are called variables, and variables can be used to hold values (x=5) or expressions (z=x+y).
VBScript Variables
As with algebra, VBScript variables are used to hold values or expressions.
A variable can have a short name, like x, or a more descriptive name, like carname.
Rules for VBScript variable names:
- Must begin with a letter
- Cannot contain a period (.)
- Cannot exceed 255 characters
In VBScript, all variables are of type variant, that can store different types of data.
Declaring (Creating) VBScript Variables
Creating variables in VBScript is most often referred to as "declaring" variables.
You can declare VBScript variables with the Dim, Public or the Private statement. Like this:
Now you have created two variables. The name of the variables are "x" and "carname".
You can also declare variables by using its name in a script. Like this:
Now you have also created a variable. The name of the variable is "carname". However, this method is not a good practice, because you can misspell the variable name later in your script, and that can cause strange results when your script is running.
If you misspell for example the "carname" variable to "carnime", the script will automatically create a new variable called "carnime". To prevent your script from doing this, you can use the Option Explicit statement. This statement forces you to declare all your variables with the dim, public or private statement.
Put the Option Explicit statement on the top of your script. Like this:
Option Explicit
Dim carname
carname=some value
Assigning Values to Variables
You assign a value to a variable like this:
The variable name is on the left side of the expression and the value you want to assign to the variable is on the right. Now the variable "carname" has the value of "Volvo", and the variable "x" has the value of "10".
VBScript Array Variables
An array variable is used to store multiple values in a single variable.
In the following example, an array containing 3 elements is declared:
The number shown in the parentheses is 2. We start at zero so this array contains 3 elements. This is a fixed-size array. You assign data to each of the elements of the array like this:
names(0)="Tove"
names(1)="Jani"
names(2)="Stale"
Similarly, the data can be retrieved from any element using the index of the particular array element you want. Like this:
You can have up to 60 dimensions in an array. Multiple dimensions are declared by separating the numbers in the parentheses with commas. Here we have a two-dimensional array consisting of 5 rows and 7 columns:
Assign data to a two-dimensional array:
Example
<% Dim x(2,2) x(0,0)="Volvo" x(0,1)="BMW" x(0,2)="Ford" x(1,0)="Apple" x(1,1)="Orange" x(1,2)="Banana" x(2,0)="Coke" x(2,1)="Pepsi" x(2,2)="Sprite" for i=0 to 2 response.write("
")
for j=0 to 2
response.write(x(i,j) & "
")
next
response.write("
") next %>
The Lifetime of Variables
A variable declared outside a procedure can be accessed and changed by any script in the ASP file.
A variable declared inside a procedure is created and destroyed every time the procedure is executed. No scripts outside the procedure can access or change the variable.
To declare variables accessible to more than one ASP file, declare them as session variables or application variables.
Session Variables
Session variables are used to store information about ONE single user, and are available to all pages in one application. Typically information stored in session variables are name, id, and preferences.
Application Variables
Application variables are also available to all pages in one application. Application variables are used to store information about ALL users in one specific application.
ASP Procedures
In ASP you can call a JavaScript procedure from a VBScript and vice versa.
Procedures
The ASP source code can contain procedures and functions:
Example
<% sub vbproc(num1,num2) response.write(num1*num2) end sub %>
Result: <%call vbproc(3,4)%>
Insert the <%@ language="language" %> line above the tag to write the procedure/function in another scripting language:
Example
<%@ language="javascript" %> <% function jsproc(num1,num2) { Response.Write(num1*num2) } %>
Result: <%jsproc(3,4)%>
Differences Between VBScript and JavaScript
When calling a VBScript or a JavaScript procedure from an ASP file written in VBScript, you can use the "call" keyword followed by the procedure name. If a procedure requires parameters, the parameter list must be enclosed in parentheses when using the "call" keyword. If you omit the "call" keyword, the parameter list must not be enclosed in parentheses. If the procedure has no parameters, the parentheses are optional.
When calling a JavaScript or a VBScript procedure from an ASP file written in JavaScript, always use parentheses after the procedure name.
VBScript Procedures
VBScript has two kinds procedures:
- Sub procedure
- Function procedure
VBScript Sub Procedures
A Sub procedure:
- is a series of statements, enclosed by the Sub and End Sub statements
- can perform actions, but does not return a value
- can take arguments
Sub mysub()
some statements
End Sub
or
Sub mysub(argument1,argument2)
some statements
End Sub
Example
Sub mysub()
response.write("I was written by a sub procedure")
End Sub
VBScript Function Procedures
A Function procedure:
- is a series of statements, enclosed by the Function and End Function statements
- can perform actions and can return a value
- can take arguments that are passed to it by a calling procedure
- without arguments, must include an empty set of parentheses ()
- returns a value by assigning a value to its name
Function myfunction()
some statements
myfunction=some value
End Function
or
Function myfunction(argument1,argument2)
some statements
myfunction=some value
End Function
Example
function myfunction()
myfunction=Date()
end function
Calling a Procedure
This simple function procedures is called to calculate the sum of two arguments:
Example
Function myfunction(a,b)
myfunction=a+b
End Function
response.write(myfunction(5,9))
The function "myfunction" will return the sum of argument "a" and argument "b". In this case 14.
When you call a procedure you can use the Call statement, like this:
Or, you can omit the Call statement, like this:
More Examples
How to call both a JavaScript procedure and a VBScript procedure in an ASP file.
Conditional Statements
Conditional statements are used to perform different actions for different decisions.
In VBScript we have four conditional statements:
- If statement - executes a set of code when a condition is true
- If...Then...Else statement - select one of two sets of lines to execute
- If...Then...ElseIf statement - select one of many sets of lines to execute
- Select Case statement - select one of many sets of lines to execute
If...Then...Else
Use the If...Then...Else statement if you want to
- execute some code if a condition is true
- select one of two blocks of code to execute
If you want to execute only one statement when a condition is true, you can write the code on one line:
If i=10 Then response.write("Hello")
There is no ..Else.. in this syntax. You just tell the code to perform one action if a condition is true (in this case If i=10).
If you want to execute more than one statement when a condition is true, you must put each statement on separate lines, and end the statement with the keyword "End If":
If i=10 Then
response.write("Hello")
i = i+1
End If
There is no ..Else.. in the example above either. You just tell the code to perform multiple actions if the condition is true.
If you want to execute a statement if a condition is true and execute another statement if the condition is not true, you must add the "Else" keyword:
Example
i=hour(time)
If i < 10 Then
response.write("Good morning!")
Else
response.write("Have a nice day!")
End If
In the example above, the first block of code will be executed if the condition is true, and the other block will be executed otherwise (if i is greater than 10).
If...Then...ElseIf
You can use the If...Then...ElseIf statement if you want to select one of many blocks of code to execute:
Example
i=hour(time)
If i = 10 Then
response.write("Just started...!")
ElseIf i = 11 Then
response.write("Hungry!")
ElseIf i = 12 Then
response.write("Ah, lunch-time!")
ElseIf i = 16 Then
response.write("Time to go home!")
Else
response.write("Unknown")
End If
Select Case
You can also use the "Select Case" statement if you want to select one of many blocks of code to execute:
Example
d=weekday(date)
Select Case d
Case 1
response.write("Sleepy Sunday")
Case 2
response.write("Monday again!")
Case 3
response.write("Just Tuesday!")
Case 4
response.write("Wednesday!")
Case 5
response.write("Thursday...")
Case 6
response.write("Finally Friday!")
Case else
response.write("Super Saturday!!!!")
End Select
This is how it works: First we have a single expression (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each Case in the structure. If there is a match, the block of code associated with that Case is executed.
Looping Statements
Looping statements are used to run the same block of code a specified number of times.
In VBScript we have four looping statements:
- For...Next statement - runs code a specified number of times
- For Each...Next statement - runs code for each item in a collection or each element of an array
- Do...Loop statement - loops while or until a condition is true
- While...Wend statement - Do not use it - use the Do...Loop statement instead
For...Next Loop
Use the For...Next statement to run a block of code a specified number of times.
The For statement specifies the counter variable (i), and its start and end values. The Next statement increases the counter variable (i) by one.
Example
<%
For i = 0 To 5
response.write("The number is " & i & "
")
Next
%>
The Step Keyword
With the Step keyword, you can increase or decrease the counter variable by the value you specify.
In the example below, the counter variable (i) is INCREASED by two, each time the loop repeats.
For i=2 To 10 Step 2
some code
Next
To decrease the counter variable, you must use a negative Step value. You must specify an end value that is less than the start value.
In the example below, the counter variable (i) is DECREASED by two, each time the loop repeats.
For i=10 To 2 Step -2
some code
Next
Exit a For...Next
You can exit a For...Next statement with the Exit For keyword.
For i=1 To 10
If i=5 Then Exit For
some code
Next
For Each...Next Loop
A For Each...Next loop repeats a block of code for each item in a collection, or for each element of an array.
Example
<%
Dim cars(2)
cars(0)="Volvo"
cars(1)="Saab"
cars(2)="BMW"
For Each x In cars
response.write(x & "
")
Next
%>
Do...Loop
If you don't know how many repetitions you want, use a Do...Loop statement.
The Do...Loop statement repeats a block of code while a condition is true, or until a condition becomes true.
Repeat Code While a Condition is True
You use the While keyword to check a condition in a Do...Loop statement.
Do While i>10
some code
Loop
If i equals 9, the code inside the loop above will never be executed.
Do
some code
Loop While i>10
The code inside this loop will be executed at least one time, even if i is less than 10.
Repeat Code Until a Condition Becomes True
You use the Until keyword to check a condition in a Do...Loop statement.
Do Until i=10
some code
Loop
If i equals 10, the code inside the loop will never be executed.
Do
some code
Loop Until i=10
The code inside this loop will be executed at least one time, even if i is equal to 10.
Exit a Do...Loop
You can exit a Do...Loop statement with the Exit Do keyword.
Do Until i=10
i=i-1
If i<10 Then Exit Do
Loop
The code inside this loop will be executed as long as i is different from 10, and as long as i is greater than 10.
More Examples
How to loop through the six headings in html.
How to make a simple Do...While loop.
The Request.QueryString and Request.Form commands are used to retrieve user input from forms.
User Input
The Request object can be used to retrieve user information from forms.
User input can be retrieved with the Request.QueryString or Request.Form command.
Request.QueryString
The Request.QueryString command is used to collect values in a form with method="get".
Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send.
Example HTML form
<form method="get" action="simpleform.asp">
First Name: <input type="text" name="fname"><br>
Last Name: <input type="text" name="lname"><br><br>
<input type="submit" value="Submit">
</form>
If a user typed "Bill" and "Gates" in the HTML form above, the URL sent to the server would look like this:
https://www.w3schools.com/simpleform.asp?fname=Bill&lname=Gates
Assume that "simpleform.asp" contains the following ASP script:
<body>
Welcome
<%
response.write(request.querystring("fname"))
response.write(" " & request.querystring("lname"))
%>
</body>
The browser will display the following in the body of the document:
Welcome Bill Gates
Request.Form
The Request.Form command is used to collect values in a form with method="post".
Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
Example HTML form
<form method="post" action="simpleform.asp">
First Name: <input type="text" name="fname"><br>
Last Name: <input type="text" name="lname"><br><br>
<input type="submit" value="Submit">
</form>
If a user typed "Bill" and "Gates" in the HTML form above, the URL sent to the server would look like this:
https://www.w3schools.com/simpleform.asp
Assume that "simpleform.asp" contains the following ASP script:
<body>
Welcome
<%
response.write(request.form("fname"))
response.write(" " & request.form("lname"))
%>
</body>
The browser will display the following in the body of the document:
Welcome Bill Gates
Form Validation
User input should be validated on the browser whenever possible (by client scripts). Browser validation is faster and reduces the server load.
You should consider server validation if the user input will be inserted into a database. A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error.
A cookie is often used to identify a user.
More Examples
How to create a Welcome cookie.
What is a Cookie?
A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With ASP, you can both create and retrieve cookie values.
How to Create a Cookie?
The "Response.Cookies" command is used to create cookies.
Note: The Response.Cookies command must appear BEFORE the <html> tag.
In the example below, we will create a cookie named "firstname" and assign the value "Alex" to it:
<%
Response.Cookies("firstname")="Alex"
%>
It is also possible to assign properties to a cookie, like setting a date when the cookie should expire:
<%
Response.Cookies("firstname")="Alex"
Response.Cookies("firstname").Expires=#May 10,2012#
%>
How to Retrieve a Cookie Value?
The "Request.Cookies" command is used to retrieve a cookie value.
In the example below, we retrieve the value of the cookie named "firstname" and display it on a page:
<%
fname=Request.Cookies("firstname")
response.write("Firstname=" & fname)
%>
Output: Firstname=Alex
A Cookie with Keys
If a cookie contains a collection of multiple values, we say that the cookie has Keys.
In the example below, we will create a cookie collection named "user". The "user" cookie has Keys that contains information about a user:
<%
Response.Cookies("user")("firstname")="John"
Response.Cookies("user")("lastname")="Smith"
Response.Cookies("user")("country")="Norway"
Response.Cookies("user")("age")="25"
%>
Read all Cookies
Look at the following code:
<%
Response.Cookies("firstname")="Alex"
Response.Cookies("user")("firstname")="John"
Response.Cookies("user")("lastname")="Smith"
Response.Cookies("user")("country")="Norway"
Response.Cookies("user")("age")="25"
%>
Assume that your server has sent all the cookies above to a user.
Now we want to read all the cookies sent to a user. The example below shows how to do it (note that the code below checks if a cookie has Keys with the HasKeys property):
<!DOCTYPE html>
<html>
<body>
<%
dim x,y
for each x in Request.Cookies
response.write("<p>")
if Request.Cookies(x).HasKeys then
for each y in Request.Cookies(x)
response.write(x & ":" & y & "=" & Request.Cookies(x)(y))
response.write("<br>")
next
else
Response.Write(x & "=" & Request.Cookies(x) & "<br>")
end if
response.write "</p>"
next
%>
</body>
</html>
Output:
firstname=Alex
user:firstname=John
user:lastname=Smith
user:country=Norway
user:age=25
What if a Browser Does NOT Support Cookies?
If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. There are two ways of doing this:
1. Add parameters to a URL
You can add parameters to a URL:
<a href="welcome.asp?fname=John&lname=Smith">Go to Welcome Page</a>
And retrieve the values in the "welcome.asp" file like this:
<%
fname=Request.querystring("fname")
lname=Request.querystring("lname")
response.write("<p>Hello " & fname & " " & lname & "!</p>")
response.write("<p>Welcome to my Web site!</p>")
%>
2. Use a form
You can use a form. The form passes the user input to "welcome.asp" when the user clicks on the Submit button:
<form method="post" action="welcome.asp">
First Name: <input type="text" name="fname" value="">
Last Name: <input type="text" name="lname" value="">
<input type="submit" value="Submit">
</form>
Retrieve the values in the "welcome.asp" file like this:
<%
fname=Request.form("fname")
lname=Request.form("lname")
response.write("<p>Hello " & fname & " " & lname & "!</p>")
response.write("<p>Welcome to my Web site!</p>")
%>
A Session object stores information about, or change settings for a user session.
The Session object
When you are working with an application on your computer, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you open the application and when you close it. However, on the internet there is one problem: the web server does not know who you are and what you do, because the HTTP address doesn't maintain state.
ASP solves this problem by creating a unique cookie for each user. The cookie is sent to the user's computer and it contains information that identifies the user. This interface is called the Session object.
The Session object stores information about, or change settings for a user session.
Variables stored in a Session object hold information about one single user, and are available to all pages in one application. Common information stored in session variables are name, id, and preferences. The server creates a new Session object for each new user, and destroys the Session object when the session expires.
When does a Session Start?
A session starts when:
- A new user requests an ASP file, and the Global.asa file includes a Session_OnStart procedure
- A value is stored in a Session variable
- A user requests an ASP file, and the Global.asa file uses the <object> tag to instantiate an object with session scope
When does a Session End?
A session ends if a user has not requested or refreshed a page in the application for a specified period. By default, this is 20 minutes.
If you want to set a timeout interval that is shorter or longer than the default, use the Timeout property.
The example below sets a timeout interval of 5 minutes:
<%
Session.Timeout=5
%>
Use the Abandon method to end a session immediately:
<%
Session.Abandon
%>
Note: The main problem with sessions is WHEN they should end. We do not know if the user's last request was the final one or not. So we do not know how long we should keep the session "alive". Waiting too long for an idle session uses up resources on the server, but if the session is deleted too soon the user has to start all over again because the server has deleted all the information. Finding the right timeout interval can be difficult!
Tip: Only store SMALL amounts of data in session variables!
Store and Retrieve Session Variables
The most important thing about the Session object is that you can store variables in it.
The example below will set the Session variable username to "Donald Duck" and the Session variable age to "50":
<%
Session("username")="Donald Duck"
Session("age")=50
%>
When the value is stored in a session variable it can be reached from ANY page in the ASP application:
Welcome <%Response.Write(Session("username"))%>
The line above returns: "Welcome Donald Duck".
You can also store user preferences in the Session object, and then access that preference to choose what page to return to the user.
The example below specifies a text-only version of the page if the user has a low screen resolution:
<%If Session("screenres")="low" Then%>
This is the text version of the page
<%Else%>
This is the multimedia version of the page
<%End If%>
Remove Session Variables
The Contents collection contains all session variables.
It is possible to remove a session variable with the Remove method.
The example below removes the session variable "sale" if the value of the session variable "age" is lower than 18:
<%
If Session.Contents("age")<18 then
Session.Contents.Remove("sale")
End If
%>
To remove all variables in a session, use the RemoveAll method:
<%
Session.Contents.RemoveAll()
%>
Loop Through the Contents Collection
The Contents collection contains all session variables. You can loop through the Contents collection, to see what's stored in it:
<%
Session("username")="Donald Duck"
Session("age")=50
dim i
For Each i in Session.Contents
Response.Write(i & "<br>")
Next
%>
Result:
username
age
If you do not know the number of items in the Contents collection, you can use the Count property:
<%
dim i
dim j
j=Session.Contents.Count
Response.Write("Session variables: " & j)
For i=1 to j
Response.Write(Session.Contents(i) & "<br>")
Next
%>
Result:
Session variables: 2
Donald Duck
50
Loop Through the StaticObjects Collection
You can loop through the StaticObjects collection, to see the values of all objects stored in the Session object:
<%
dim i
For Each i in Session.StaticObjects
Response.Write(i & "<br>")
Next
%>
A group of ASP files that work together to perform some purpose is called an application. The Application object is used to tie these files together.
Application Object
An application on the Web may consists of several ASP files that work together to perform some purpose. The Application object is used to tie these files together.
The Application object is used to store and access variables from any page, just like the Session object. The difference is that ALL users share ONE Application object (with Sessions there is ONE Session object for EACH user).
The Application object holds information that will be used by many pages in the application (like database connection information). The information can be accessed from any page. The information can also be changed in one place, and the changes will automatically be reflected on all pages.
The Application object's collections, methods, and events are described below:
Collections
|
Collection
|
Description
|
|
Contents
|
Contains all the items appended to the application through a script command
|
|
StaticObjects
|
Contains all the objects appended to the application with the HTML <object> tag
|
Methods
|
Method
|
Description
|
|
Contents.Remove
|
Deletes an item from the Contents collection
|
|
Contents.RemoveAll()
|
Deletes all items from the Contents collection
|
|
Lock
|
Prevents other users from modifying the variables in the Application object
|
|
Unlock
|
Enables other users to modify the variables in the Application object (after it has been locked using the Lock method)
|
Events
|
Event
|
Description
|
|
Application_OnEnd
|
Occurs when all user sessions are over, and the application ends
|
|
Application_OnStart
|
Occurs before the first new session is created (when the Application object is first referenced)
|
The #include Directive
You can insert the content of one ASP file into another ASP file before the server executes it, with the #include directive.
The #include directive is used to create functions, headers, footers, or elements that will be reused on multiple pages.
How to Use the #include Directive
Here is a file called "mypage.asp":
<!DOCTYPE html>
<html>
<body>
<h3>Words of Wisdom:</h3>
<p><!--#include file="wisdom.inc"--></p>
<h3>The time is:</h3>
<p><!--#include file="time.inc"--></p>
</body>
</html>
Here is the "wisdom.inc" file:
"One should never increase, beyond what is necessary,
the number of entities required to explain anything."
Here is the "time.inc" file:
<%
Response.Write(Time)
%>
If you look at the source code in a browser, it will look something like this:
<!DOCTYPE html>
<html>
<body>
<h3>Words of Wisdom:</h3>
<p>"One should never increase, beyond what is necessary,
the number of entities required to explain anything."</p>
<h3>The time is:</h3>
<p>11:33:42 AM</p>
</body>
</html>
Syntax for Including Files
To include a file in an ASP page, place the #include directive inside comment tags:
<!--#include virtual="somefilename"-->
or
<!--#include file ="somefilename"-->
The Virtual Keyword
Use the virtual keyword to indicate a path beginning with a virtual directory.
If a file named "header.inc" resides in a virtual directory named /html, the following line would insert the contents of "header.inc":
<!-- #include virtual ="/html/header.inc" -->
The File Keyword
Use the file keyword to indicate a relative path. A relative path begins with the directory that contains the including file.
If you have a file in the html directory, and the file "header.inc" resides in htmlheaders, the following line would insert "header.inc" in your file:
<!-- #include file ="headersheader.inc" -->
Note that the path to the included file (headersheader.inc) is relative to the including file. If the file containing this #include statement is not in the html directory, the statement will not work.
Tips and Notes
In the sections above we have used the file extension ".inc" for included files. Notice that if a user tries to browse an INC file directly, its content will be displayed. If your included file contains confidential information or information you do not want any users to see, it is better to use an ASP extension. The source code in an ASP file will not be visible after the interpretation. An included file can also include other files, and one ASP file can include the same file more than once.
Important: Included files are processed and inserted before the scripts are executed. The following script will NOT work because ASP executes the #include directive before it assigns a value to the variable:
<%
fname="header.inc"
%>
<!--#include file="<%fname%>"-->
You cannot open or close a script delimiter in an INC file. The following script will NOT work:
<%
For i = 1 To n
<!--#include file="count.inc"-->
Next
%>
But this script will work:
<% For i = 1 to n %>
<!--#include file="count.inc" -->
<% Next %>
The Global.asa file
The Global.asa file is an optional file that can contain declarations of objects, variables, and methods that can be accessed by every page in an ASP application.
All valid browser scripts (JavaScript, VBScript, JScript, PerlScript, etc.) can be used within Global.asa.
The Global.asa file can contain only the following:
- Application events
- Session events
- <object> declarations
- TypeLibrary declarations
- the #include directive
Note: The Global.asa file must be stored in the root directory of the ASP application, and each application can only have one Global.asa file.
Events in Global.asa
In Global.asa you can tell the application and session objects what to do when the application/session starts and what to do when the application/session ends. The code for this is placed in event handlers. The Global.asa file can contain four types of events:
Application_OnStart - Occurs when the FIRST user calls the first page in an ASP application. This event occurs after the Web server is restarted or after the Global.asa file is edited. The "Session_OnStart" event occurs immediately after this event.
Session_OnStart - This event occurs EVERY time a NEW user requests his or her first page in the ASP application.
Session_OnEnd - This event occurs EVERY time a user ends a session. A user-session ends after a page has not been requested by the user for a specified time (by default this is 20 minutes).
Application_OnEnd - This event occurs after the LAST user has ended the session. Typically, this event occurs when a Web server stops. This procedure is used to clean up settings after the Application stops, like delete records or write information to text files.
A Global.asa file could look something like this:
<script language="vbscript" runat="server">
sub Application_OnStart
'some code
end sub
sub Application_OnEnd
'some code
end sub
sub Session_OnStart
'some code
end sub
sub Session_OnEnd
'some code
end sub
</script>
Note: Because we cannot use the ASP script delimiters (<% and %>) to insert scripts in the Global.asa file, we put subroutines inside an HTML <script> element.
<object> Declarations
It is possible to create objects with session or application scope in Global.asa by using the <object> tag.
Note: The <object> tag should be outside the <script> tag!
Syntax
<object runat="server" scope="scope" id="id" {progid="progID"|classid="classID"}>
....
</object>
| Parameter |
Description |
| scope |
Sets the scope of the object (either Session or Application) |
| id |
Specifies a unique id for the object |
| ProgID |
An id associated with a class id. The format for ProgID is [Vendor.]Component[.Version]
Either ProgID or ClassID must be specified.
|
| ClassID |
Specifies a unique id for a COM class object.
Either ProgID or ClassID must be specified.
|
Examples
The first example creates an object of session scope named "MyAd" by using the ProgID parameter:
<object runat="server" scope="session" id="MyAd" progid="MSWC.AdRotator">
</object>
The second example creates an object of application scope named "MyConnection" by using the ClassID parameter:
<object runat="server" scope="application" id="MyConnection"
classid="Clsid:8AD3067A-B3FC-11CF-A560-00A0C9081C21">
</object>
The objects declared in the Global.asa file can be used by any script in the application:
GLOBAL.ASA:
<object runat="server" scope="session" id="MyAd" progid="MSWC.AdRotator">
</object>
You could reference the object "MyAd" from any page in the ASP application:
SOME .ASP FILE:
<%=MyAd.GetAdvertisement("/banners/adrot.txt")%>
TypeLibrary Declarations
A TypeLibrary is a container for the contents of a DLL file corresponding to a COM object. By including a call to the TypeLibrary in the Global.asa file, the constants of the COM object can be accessed, and errors can be better reported by the ASP code. If your Web application relies on COM objects that have declared data types in type libraries, you can declare the type libraries in Global.asa.
Syntax
<!--METADATA TYPE="TypeLib"
file="filename" uuid="id" version="number" lcid="localeid"
-->
| Parameter |
Description |
| file |
Specifies an absolute path to a type library.
Either the file parameter or the uuid parameter is required
|
| uuid |
Specifies a unique identifier for the type library.
Either the file parameter or the uuid parameter is required
|
| version |
Optional. Used for selecting version. If the requested version is not found, then the most recent version is used |
| lcid |
Optional. The locale identifier to be used for the type library |
Error Values
The server can return one of the following error messages:
| Error Code |
Description |
| ASP 0222 |
Invalid type library specification |
| ASP 0223 |
Type library not found |
| ASP 0224 |
Type library cannot be loaded |
| ASP 0225 |
Type library cannot be wrapped |
Note: METADATA tags can appear anywhere in the Global.asa file (both inside and outside <script> tags). However, it is recommended that METADATA tags appear near the top of the Global.asa file.
Restrictions
Restrictions on what you can include in the Global.asa file:
- You cannot display text written in the Global.asa file. This file can't display information
- You can only use Server and Application objects in the Application_OnStart and Application_OnEnd subroutines. In the Session_OnEnd subroutine, you can use Server, Application, and Session objects. In the Session_OnStart subroutine you can use any built-in object
How to use the Subroutines
Global.asa is often used to initialize variables.
The example below shows how to detect the exact time a visitor first arrives on a Web site. The time is stored in a Session variable named "started", and the value of the "started" variable can be accessed from any ASP page in the application:
<script language="vbscript" runat="server">
sub Session_OnStart
Session("started")=now()
end sub
</script>
Global.asa can also be used to control page access.
The example below shows how to redirect every new visitor to another page, in this case to a page called "newpage.asp":
<script language="vbscript" runat="server">
sub Session_OnStart
Response.Redirect("newpage.asp")
end sub
</script>
And you can include functions in the Global.asa file.
In the example below the Application_OnStart subroutine occurs when the Web server starts. Then the Application_OnStart subroutine calls another subroutine named "getcustomers". The "getcustomers" subroutine opens a database and retrieves a record set from the "customers" table. The record set is assigned to an array, where it can be accessed from any ASP page without querying the database:
<script language="vbscript" runat="server">
sub Application_OnStart
getcustomers
end sub
sub getcustomers
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open "c:/webdata/northwind.mdb"
set rs=conn.execute("select name from customers")
Application("customers")=rs.GetRows
rs.Close
conn.Close
end sub
</script>
Global.asa Example
In this example we will create a Global.asa file that counts the number of current visitors.
- The Application_OnStart sets the Application variable "visitors" to 0 when the server starts
- The Session_OnStart subroutine adds one to the variable "visitors" every time a new visitor arrives
- The Session_OnEnd subroutine subtracts one from "visitors" each time this subroutine is triggered
The Global.asa file:
<script language="vbscript" runat="server">
Sub Application_OnStart
Application("visitors")=0
End Sub
Sub Session_OnStart
Application.Lock
Application("visitors")=Application("visitors")+1
Application.UnLock
End Sub
Sub Session_OnEnd
Application.Lock
Application("visitors")=Application("visitors")-1
Application.UnLock
End Sub
</script>
To display the number of current visitors in an ASP file:
<!DOCTYPE html> <html> <head> </head> <body> <p>There are <%response.write(Application("visitors"))%> online now!</p> </body> </html>
AJAX is about updating parts of a web page, without reloading the whole page.
What is AJAX?
AJAX = Asynchronous JavaScript and XML.
AJAX is a technique for creating fast and dynamic web pages.
AJAX allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page.
Classic web pages, (which do not use AJAX) must reload the entire page if the content should change.
Examples of applications using AJAX: Google Maps, Gmail, Youtube, and Facebook tabs.
How AJAX Works
AJAX is Based on Internet Standards
AJAX is based on internet standards, and uses a combination of:
- XMLHttpRequest object (to exchange data asynchronously with a server)
- JavaScript/DOM (to display/interact with the information)
- CSS (to style the data)
- XML (often used as the format for transferring data)
AJAX applications are browser- and platform-independent!
Google Suggest
AJAX was made popular in 2005 by Google, with Google Suggest.
Google Suggest is using AJAX to create a very dynamic web interface: When you start typing in Google's search box, a JavaScript sends the letters off to a server and the server returns a list of suggestions.
Start Using AJAX Today
In our ASP tutorial, we will demonstrate how AJAX can update parts of a web page, without reloading the whole page. The server script will be written in ASP.
If you want to learn more about AJAX, visit our
AJAX ASP Example
The following example will demonstrate how a web page can communicate with a web server while a user type characters in an input field:
Example
Start typing a name in the input field below:
First name:
Suggestions:
Example Explained
In the example above, when a user types a character in the input field, a function called "showHint()" is executed.
The function is triggered by the onkeyup event.
Here is the HTML code:
Example
<html>
<head>
<script>
function showHint(str) {
if (str.length == 0) {
document.getElementById("txtHint").innerHTML = "";
return;
} else {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("txtHint").innerHTML = this.responseText;
}
};
xmlhttp.open("GET", "gethint.asp?q=" + str, true);
xmlhttp.send();
}
}
</script>
</head>
<body>
<p><b>Start typing a name in the input field below:</b></p>
<form>
First name: <input type="text" onkeyup="showHint(this.value)">
</form>
<p>Suggestions: <span id="txtHint"></span></p>
</body>
</html>
Code explanation:
First, check if the input field is empty (str.length == 0). If it is, clear the content of the txtHint placeholder and exit the function.
However, if the input field is not empty, do the following:
- Create an XMLHttpRequest object
- Create the function to be executed when the server response is ready
- Send the request off to an ASP file (gethint.asp) on the server
- Notice that q parameter is added gethint.asp?q="+str
- The str variable holds the content of the input field
The ASP File - "gethint.asp"
The ASP file checks an array of names, and returns the corresponding name(s) to the browser:
<%
response.expires=-1
dim a(30)
'Fill up array with names
a(1)="Anna"
a(2)="Brittany"
a(3)="Cinderella"
a(4)="Diana"
a(5)="Eva"
a(6)="Fiona"
a(7)="Gunda"
a(8)="Hege"
a(9)="Inga"
a(10)="Johanna"
a(11)="Kitty"
a(12)="Linda"
a(13)="Nina"
a(14)="Ophelia"
a(15)="Petunia"
a(16)="Amanda"
a(17)="Raquel"
a(18)="Cindy"
a(19)="Doris"
a(20)="Eve"
a(21)="Evita"
a(22)="Sunniva"
a(23)="Tove"
a(24)="Unni"
a(25)="Violet"
a(26)="Liza"
a(27)="Elizabeth"
a(28)="Ellen"
a(29)="Wenche"
a(30)="Vicky"
'get the q parameter from URL
q=ucase(request.querystring("q"))
'lookup all hints from array if length of q>0
if len(q)>0 then
hint=""
for i=1 to 30
if q=ucase(mid(a(i),1,len(q))) then
if hint="" then
hint=a(i)
else
hint=hint & " , " & a(i)
end if
end if
next
end if
'Output "no suggestion" if no hint were found
'or output the correct values
if hint="" then
response.write("no suggestion")
else
response.write(hint)
end if
%>
AJAX can be used for interactive communication with a database.
AJAX Database Example
The following example will demonstrate how a web page can fetch information from a database with AJAX:
Example
Select a customer: Alfreds Futterkiste North/South Wolski Zajazd
Customer info will be listed here...
Example Explained - The HTML Page
When a user selects a customer in the dropdown list above, a function called "showCustomer()" is executed. The function is triggered by the "onchange" event:
<!DOCTYPE html>
<html>
<head>
<script>
function showCustomer(str)
{
if (str=="")
{
document.getElementById("txtHint").innerHTML="";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (this.readyState==4 && this.status==200)
{
document.getElementById("txtHint").innerHTML=this.responseText;
}
}
xmlhttp.open("GET","getcustomer.asp?q="+str,true);
xmlhttp.send();
}
</script>
</head
<body>
<form>
<select name="customers" onchange="showCustomer(this.value)">
<option value="">Select a customer:</option>
<option value="ALFKI">Alfreds Futterkiste</option>
<option value="NORTS ">North/South</option>
<option value="WOLZA">Wolski Zajazd</option>
</select>
</form>
<
<div id="txtHint">Customer info will be listed here...</div>
</body>
</html>
Source code explanation:
If no customer is selected (str.length==0), the function clears the content of the txtHint placeholder and exits the function.
If a customer is selected, the showCustomer() function executes the following:
- Create an XMLHttpRequest object
- Create the function to be executed when the server response is ready
- Send the request off to a file on the server
- Notice that a parameter (q) is added to the URL (with the content of the dropdown list)
The ASP File
The page on the server called by the JavaScript above is an ASP file called "getcustomer.asp".
The source code in "getcustomer.asp" runs a query against a database, and returns the result in an HTML table:
<%
response.expires=-1
sql="SELECT * FROM CUSTOMERS WHERE CUSTOMERID="
sql=sql & "'" & request.querystring("q") & "'"
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open(Server.Mappath("/datafolder/northwind.mdb"))
set rs=Server.CreateObject("ADODB.recordset")
rs.Open sql,conn
response.write("<table>")
do until rs.EOF
for each x in rs.Fields
response.write("<tr><td><b>" & x.name & "</b></td>")
response.write("<td>" & x.value & "</td></tr>")
next
rs.MoveNext
loop
response.write("</table>")
%>
CDOSYS is a built-in component in ASP. This component is used to send e-mails with ASP.
Sending e-mail with CDOSYS
CDO (Collaboration Data Objects) is a Microsoft technology that is designed to simplify the creation of messaging applications.
CDOSYS is a built-in component in ASP. We will show you how to use this component to send e-mail with ASP.
How about CDONTs?
Microsoft has discontinued the use of CDONTs on Windows 2000, Windows XP and Windows 2003. If you have used CDONTs in your ASP applications, you should update the code and use the new CDO technology.
Examples using CDOSYS
Sending a text e-mail:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.TextBody = "This is a message."
myMail.Send
set myMail = nothing
%>
Sending a text e-mail with Bcc and CC fields:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.Bcc = "[email protected]"
myMail.Cc = "[email protected]"
myMail.TextBody = "This is a message."
myMail.Send
set myMail = nothing
%>
Sending an HTML e-mail:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.HTMLBody = "<h1>This is a message.</h1>"
myMail.Send
set myMail = nothing
%>
Sending an HTML e-mail that sends a webpage from a website:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To ="[email protected]"
myMail.CreateMHTMLBody "https://www.w3schools.com/asp/"
myMail.Send
set myMail = nothing
%>
Sending an HTML e-mail that sends a webpage from a file on your computer:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.CreateMHTMLBody "file://c:/mydocuments/test.htm"
myMail.Send
set myMail = nothing
%>
Sending a text e-mail with an Attachment:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.TextBody = "This is a message."
myMail.AddAttachment "c:mydocumentstest.txt"
myMail.Send
set myMail = nothing
%>
Sending a text e-mail using a remote server:
<%
Set myMail = CreateObject("CDO.Message")
myMail.Subject = "Sending email with CDO"
myMail.From = "[email protected]"
myMail.To = "[email protected]"
myMail.TextBody = "This is a message."
myMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
'Name or IP of remote SMTP server
myMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "smtp.server.com"
'Server port
myMail.Configuration.Fields.Item _
("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
myMail.Configuration.Fields.Update
myMail.Send
set myMail = nothing
%>
ASP and VBScript Examples
ASP Output
VbScript Variables
VBScript Looping
VBScript Date and Time Functions
Some Other Built-in VBScript Functions
Procedures
VBScript vs JavaScript
VBScript Conditional Statements
ASP Forms
ASP Cookies
ASP Response Object
ASP Request Object
ASP Session Object
ASP Server Object
ASP FileSystem Object
ASP TextStream Object
ASP Drive Object
ASP File Object
ASP Dictionary Object
ASP AdRotator
ASP Browser Capabilities
ASP ContentRotator
ASP Content Linking
ADO Display
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