ASP.NET - First Example

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An ASP.Net page is made of number of server controls along with the HTML controls, text and images. Sensitive data from the page and the states of different controls on the page are stored in hidden fields and forms the context of that page request.

ASP.Net runtime controls all association between a page instance and its state. An ASP.Net page is an object of the Page Class or inherited from it.

All the controls on the pages are also objects of the related control class inherited from a parent Control class. When a page is run an instance of the page object is created along with all its content controls.

An ASP.Net page is also a server side file saved with the .aspx extension. It is modular in nature and can be divided into the following core sections:

  • Page directives

  • Code Section

  • Page Layout

Page directives:

The page directives set up the environments for the page to run. The @Page directive defines page-specific attributes used by the ASP.Net page parser and compiler. Page directives specify how the page should be processed, and which assumptions are to be taken about the page.

It allows importing namespaces, loading assemblies and registering new controls with custom tag names and namespace prefixes. We will discuss all of these concepts in due time.

Code Section:

The code section provides the handlers for the page and control events along with other functions required. We mentioned that, ASP.Net follows an object model. Now, these objects raises events when something happens on the user interface, like a user clicks a button or moves the cursor. How these events should be handled? That code is provided in the event handlers of the controls, which are nothing but functions bound to the controls.

The code section or the code behind file provides all these event handler routines, and other functions used by the developer. The page code could be precompiled and deployed in the form of a binary assembly.

Page Layout:

The page layout provides the interface of the page. It contains the server controls, text, inline JavaScript and HTML tags:

The following code snippet provides a sample ASP.Net page explaining Page directives, code section and page layout written in C#:

<!-- directives -->
<% @Page Language="C#" %>

<!-- code section -->
<script runat="server">
private void convertoupper(object sender, EventArgs e)
{
	string str = mytext.Value;
	changed_text.InnerHtml = str.ToUpper();
}
</script>

<!-- Layout -->
<html>
<head> <title> Change to Upper Case </title> </head>
<body>
<h3> Conversion to Upper Case </h3>
<form runat="server">
	<input runat="server" id="mytext" type="text" />
	<input runat="server" id="button1" type="submit" 
    value="Enter..." OnServerClick="convertoupper"/>
<hr />
<h3> Results: </h3>
<span runat="server" id="changed_text" />
</form>
</body>
</html>

Copy this file to the web server's root directory. Generally it is c:\inetput\wwwroot. Open the file from the browser to run it and it should generate following result:

ASP.NET First Example

Using Visual Studio IDE:

Let us develop the same example using Visual Studio IDE. Instead of typing the code, you can just drag the controls into the design view:

ASP.NET First Example 2

The content file is automatically developed. All you need to add is the Button1_Click routine, which is as follows:

protected void Button1_Click(object sender, EventArgs e)
{
     string buf = TextBox1.Text;
     changed_text.InnerHtml = buf.ToUpper();
}

The content file code is:

<%@ Page Language="C#" AutoEventWireup="true" 
                       CodeBehind="Default.aspx.cs" 
                       Inherits="firstexample._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
   <form id="form1" runat="server">
   <div>
      <asp:TextBox ID="TextBox1" runat="server" style="width:224px">
      </asp:TextBox>
      <br />
      <br />
      <asp:Button ID="Button1" runat="server" Text="Enter..." 
                  style="width:85px" onclick="Button1_Click" />
      <hr />
      <h3> Results: </h3>
      <span runat="server" id="changed_text" />
   </div>
   </form>
</body>
</html>

Run the example either from Debug menu, or by pressing Ctrl-F5 or by right clicking on the design view and choosing 'View in Browser' from the popup menu. This should generate following result:

ASP.NET First Example 3


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