CodeProject: Behind the scenes of ASPX files. Free source code and programming help

Prize winner in Competition "ASP.NET Dec 2003"

Report Article

Discuss

Send to a friend

30 votes for this Article.

Popularity: 6.50 Rating: 4.40 out of 5

Introduction

ASP.NET pages are usually compound of two files: the ASPX which contains the page visualization declaration and the *.cs which contains the code to handle page events (Code behind). While all the *.cs files compile into one DLL (with the application name) and the page life cycle is well documented, this is not the case of ASPX files.

What has really happened to those ASPX files?

Well, what has really happened to those ASPX files? At the end of the day, ASP.NET turns each ASPX file into assembly. While the page is termed for the first time as ASP.NET, this leads to the:

Generation of a *.cs file holding code that matches the ASPX declarations.
Using of csc.exe (C# compiler) to compile *.cs file into DLL (you can see csc.exe if you monitor running processes).
Running of the compiled DLL

This sequence occurs just once then, resulting with DLL that will be used for other requests until one of the page dependencies files will be changed leading to the re-enforcement of the sequence. If you ever wonder why running an application for the first time takes such a long while, you would probably have some idea already.

To understand better what is going on here, let’s take a very simple page and follow the following steps. I have created a simple page that holds a Panel, Textbox and server side script inside an ASPX file. Below you can see the ASPX file:

<%@ Import Namespace="System.Web" %>
<%@ Page language="c#" Codebehind="WebForm13.aspx.cs" 
  AutoEventWireup="false" Inherits="WebApplication22.WebForm13" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm13</title>
<meta content="Microsoft Visual Studio 7.0" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" 
                                            name="vs_targetSchema">
</HEAD>
<body MS_POSITIONING="GridLayout">
<script language="C#" runat="server">
private void myfunc(object sender, System.EventArgs e)
{
  HttpContext.Current.Response.Write("Text Init"); 
}
</script>
<form id="WebForm13" method="post" runat="server">
<asp:TextBox id="TextBox1" OnLoad="myfunc" 
  style="Z-INDEX: 101; LEFT: 101px; POSITION: absolute; TOP: 114px" 
  runat="server" Width="170px" Height="48px"></asp:TextBox>
<asp:Panel id="LblNav" 
  style="Z-INDEX: 102; LEFT: 22px; POSITION: absolute; TOP: 63px" 
  runat="server" Width="269px">Panel</asp:Panel>
</form>
</body>
</HTML>

All the files that ASP.NET generated will be placed in this folder: C:\$WINDOWSDir$\Microsoft.NET\Framework\v1.0.3705\Temporary ASP.NET Files\$YourWebAppName$\42343\654564. The last two folders are randomly numbered, generated by ASP.NET. The fun begins from the last directory. That folder holds all the files generated for ASPX files, ASCX files (user control) and ASAX files. The last folder also contains a folder called Assembly that holds another directory: dl2. The dl2 folder contains sub folders with randomly numbered names each for every referenced assembly from the web project, including the application DLL. We will focus on the folder that contains all the files generated for ASPX, ASCX and ASAX files.

The first file that we’re interested in is the XML file holding the page name (WebForm13.aspx.4689d8a0.xml). This file contains information that map between the web page name and the random name that will be used by ASP.NET to generate page files. Besides the mapping information, the file consists of data on the decency files of that page (any changes of that file will cause recreation of ASPX files and recompilation):

<preserve assem="jibrfh34" type="ASP.WebForm13_aspx" hash="49b238a170c332">
<filedep name="c:\inetpub\wwwroot\WebApplication22\bin\WebApplication22.DLL" />
<filedep name="c:\inetpub\wwwroot\WebApplication22\WebForm13.aspx" />
</preserve>

After understanding that every file starting with “jibrfh34” is a file that was generated for a certain page, we should examine what is the purpose of every file. The most important file is the *.cs which holds the generated C# lines corresponding to the ASPX tags and code, but we will come back to that later. The *.res file holds resources that the compiler will use then. The *.cmdline holds the command line that will be used by ASP.NET to compile the *.cs file. The *.cmdline file includes a reference to other assemblies and optimization settings. The *.err file contains errors (if they occurred while compiling the *.cs file). The *.out file consists of outputs from the compilation process. The *.dll and *.pdb obviously function as the compilation output.

Our next step will be then exploring the *.cs file:

namespace ASP {
using System;
using System.Collections;
using System.Collections.Specialized;
using System.Configuration;
using System.Text;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Caching;
using System.Web.SessionState;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using ASP;


[System.Runtime.CompilerServices.CompilerGlobalScopeAttribute()]
public class WebForm13_aspx : WebApplication22.WebForm13, 
  System.Web.SessionState.IRequiresSessionState {


#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
  protected System.Web.UI.HtmlControls.HtmlForm WebForm13;

#line default

  private static bool __intialized = false;

  private static object __stringResource;

  private static System.Collections.ArrayList __fileDependencies;


#line 13 "http://localhost/WebApplication22/WebForm13.aspx"

  private void myfunc(object sender, System.EventArgs e)
  {
    HttpContext.Current.Response.Write("Text Init"); 
  }

#line default

  public WebForm13_aspx() {
    System.Collections.ArrayList dependencies;
    if ((ASP.WebForm13_aspx.__intialized == false)) {
      ASP.WebForm13_aspx.__stringResource = 
        System.Web.UI.TemplateControl.ReadStringResource(typeof(ASP.WebForm13_aspx));
      dependencies = new System.Collections.ArrayList();
      dependencies.Add("c:\\inetpub\\wwwroot\\WebApplication22\\WebForm13.aspx");
      ASP.WebForm13_aspx.__fileDependencies = dependencies;
      ASP.WebForm13_aspx.__intialized = true;
    }
    this.Server.ScriptTimeout = 30000000;
  }

  protected override bool SupportAutoEvents {
    get {
      return false;
    }
  }

  protected ASP.Global_asax ApplicationInstance {
    get {
      return ((ASP.Global_asax)(this.Context.ApplicationInstance));
    }
  }

  public override string TemplateSourceDirectory {
    get {
      return "/WebApplication22";
    }
  }

  private System.Web.UI.Control __BuildControlTextBox1() {
    System.Web.UI.WebControls.TextBox __ctrl;

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl = new System.Web.UI.WebControls.TextBox();

#line default
    this.TextBox1 = __ctrl;

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.ID = "TextBox1";

#line default

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    ((System.Web.UI.IAttributeAccessor)(__ctrl)).SetAttribute("style", 
      "Z-INDEX: 101; LEFT: 101px; POSITION: absolute; TOP: 114px");

#line default

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Width = System.Web.UI.WebControls.Unit.Parse("170px", 
      System.Globalization.CultureInfo.InvariantCulture);

#line default

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Height = System.Web.UI.WebControls.Unit.Parse("48px", 
      System.Globalization.CultureInfo.InvariantCulture);

#line default

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Load -= new System.EventHandler(this.myfunc);

#line default

#line 20 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Load += new System.EventHandler(this.myfunc);

#line default
    return __ctrl;
  }

  private System.Web.UI.Control __BuildControlLblNav() {
    System.Web.UI.WebControls.Panel __ctrl;

#line 21 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl = new System.Web.UI.WebControls.Panel();

#line default
    this.LblNav = __ctrl;

#line 21 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.ID = "LblNav";

#line default

#line 21 "http://localhost/WebApplication22/WebForm13.aspx"
    ((System.Web.UI.IAttributeAccessor)(__ctrl)).SetAttribute("style", 
      "Z-INDEX: 102; LEFT: 22px; POSITION: absolute; TOP: 63px");

#line default

#line 21 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Width = System.Web.UI.WebControls.Unit.Parse("269px", 
      System.Globalization.CultureInfo.InvariantCulture);

#line default
    System.Web.UI.IParserAccessor __parser = 
      ((System.Web.UI.IParserAccessor)(__ctrl));

#line 21 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(new System.Web.UI.LiteralControl("Panel"));

#line default
    return __ctrl;
  }

  private System.Web.UI.Control __BuildControlWebForm13() {
    System.Web.UI.HtmlControls.HtmlForm __ctrl;

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl = new System.Web.UI.HtmlControls.HtmlForm();

#line default
    this.WebForm13 = __ctrl;

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.ID = "WebForm13";

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __ctrl.Method = "post";

#line default
    System.Web.UI.IParserAccessor __parser = 
      ((System.Web.UI.IParserAccessor)(__ctrl));

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(new 
      System.Web.UI.LiteralControl("\r\n\t\t\t"));

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    this.__BuildControlTextBox1();

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(this.TextBox1);

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(new 
      System.Web.UI.LiteralControl("\r\n\t\t\t"));

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    this.__BuildControlLblNav();

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(this.LblNav);

#line default

#line 19 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(new 
      System.Web.UI.LiteralControl("\r\n\t\t"));

#line default
    return __ctrl;
  }

  private void __BuildControlTree(System.Web.UI.Control __ctrl) {
    System.Web.UI.IParserAccessor __parser = 
      ((System.Web.UI.IParserAccessor)(__ctrl));

#line 1 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(this.CreateResourceBasedLiteralControl(0, 397, true));

#line default

#line 1 "http://localhost/WebApplication22/WebForm13.aspx"
    this.__BuildControlWebForm13();

#line default

#line 1 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(this.WebForm13);

#line default

#line 1 "http://localhost/WebApplication22/WebForm13.aspx"
    __parser.AddParsedSubObject(new 
        System.Web.UI.LiteralControl("\r\n\r\n\t</body>\r\n</HTML>\r\n"));

#line default
  }

  protected override void FrameworkInitialize() {
    SetStringResourcePointer(ASP.WebForm13_aspx.__stringResource, 397);
    this.__BuildControlTree(this);
    this.FileDependencies = ASP.WebForm13_aspx.__fileDependencies;
    this.EnableViewStateMac = true;
  }

  public override int GetTypeHashCode() {
    return 423941586;
  }
}
}

You can notice that the file contains notes that map the code to the HTML lines in the source ASPX file. You can use those lines to see how ASP.NET converts HTML lines and learn a lot from it.

Every generated *.cs file is a definition of a class that inherits from the code behind class and implement interface:

public class WebForm13_aspx : WebApplication22.WebForm13
  System.Web.SessionState.IRequiresSessionState

This class (WebForm13_aspx) will be called before the code behind class (WebApplication22.WebForm13). Obviously WebForm13_aspx class constructor will be called first. WebForm13_aspx constructor initializes the class dependencies files. The first function to be called is FrameworkInitialize. FrameworkInitialize is a protected function declared in TemplateControl class and implemented just in ASPX file classes. FrameworkInitialize calls __BuildControlTree which is the function that is responsible to create all the page controls. __BuildControlTree calls __ BuildControlWebForm13 that creates the Form and calls __BuildControlXXX for every control on the Form. If control holds child controls, a call will be made to the corresponding __BuildControlXXX of every child control. Every __BuildControlXXX function creates object by the ASPX declaration of the corresponding control, sets its attribute and attaches all events that are declared on the ASPX file. Every function, declared in ASPX file inside SCRIPT block with runat server attribute set to true, generates as class method and connects to the corresponding delegate, if needed.

As I mentioned before, the *.CS file is compiled into assembly in the first instance the ASP.NET is calling a page. More then once, I have observed that changes made in the ASPX file are not reflected in the HTML send to the browser. In such a scenario, deleting the files under the right folder under Temporary ASP.NET will solve the problem since all the files will be recreated. Another issue that you should be aware of is that the events of control initialization in C# do not happen in the code behind file but work perfectly in the ASPX code.

After understanding what goes with ASPX files, we should go back to the page life cycle and update it. There are two classes in that process:

The code behind class – WebForm1.
The generated class for ASPX file – adbdef.

The call orders are:

Construction of adbdef.
Construction of WebForm1.
FrameworkInitialize method of adbdef class will be called.
Calling __ BuildTree and other control build functions.
Calling the Page and controls' events by their order. If event is declared in ASPX file and code behind, the ASPX event will be called first followed by the code behind event.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Natty Gur

Read my blog

http://weblogs.asp.net/ngur

Natty Gur is the founder and CTO of “The enterprise architects group” an international enterprise architecture consulting group based in Vestal, NY. Natty has 13 years of experience in the IT field, 7 of them focused on running enterprise architecture in companies and governmental bodies. Natty has written many articles and is a well known speaker on EA topics. You can reach natty at: natty@theeagroup.net

Occupation: Web Developer

Location: Israel

Other popular ASP.NET articles:

Multiple File Upload With Progress Bar Using Flash and ASP.NET
How to use Flash to upload multiple files in a medium-trust hosting environment
CAPTCHA Image
Using CAPTCHA images to prevent automated form submission.
10 ASP.NET Performance and Scalability Secrets
10 easy ways to make ASP.NET and AJAX websites faster, more scalable and support more traffic at lower cost
Paging of Large Resultsets in ASP.NET
An article about optimization and performance testing of MS SQL Server 2000 stored procedures used for paging of large resultsets in ASP.NET
File Upload with ASP.NET
This article shows you how work with uploading of the files using ASP.NET and C#.

Article Top

You must Sign In to use this message board.

Msgs 1 to 13 of 13 (Total in Forum: 13) (Refresh)

FirstPrevNext

Handle to web page

madx_hu

18:09 13 Nov '06

Can anybody tell me how can we gain handles of web page or Is it possible to implement/use window messages when we are developing an application in ASP.net Basically i want a substitute of "Windows.form.handle as IntPtr " (which is used in desktop application) AND "Application.RemoveMessageFilter" in ASP.net Thanks shaeron
Sign In·View Thread·PermaLink

AJAX

Walter O Dias

10:19 5 May '06

Hi, I'm have developer a AJAX Base Page. When i'm execute the method Activator.CreateInstance, the command is succeful and the see the methods but the componenets dont load when CreateInstance is call. How I can create the components that are in the form? Sorry by english
Sign In·View Thread·PermaLink

dynamically switching templates

rlnd

6:43 7 Jan '05

Hi, very interesting article! I have a related question (or at least I think it might be a related question). I wonder if it's possible to change the template (.aspx file) in code (in the .aspx.cs file) and use that template instead of the default .aspx file, so I can use different layouts without having to duplicate the source code. Greetings, Roland
Sign In·View Thread·PermaLink

Re: dynamically switching templates

Natty Gur

7:35 7 Jan '05

I think that what you are looking for is ASP.NET 2.0 Master Page, isn't it?
Sign In·View Thread·PermaLink

Re: dynamically switching templates

rlnd

0:47 10 Jan '05

Yes, you're right, thank you! I looked up some information on the master page feature of asp.net 2.0 and it has just the functionality I'm looking for. But I'll wait until 2.0 gets out of beta status though... Greetings, Roland
Sign In·View Thread·PermaLink

Re: dynamically switching templates

Danny Rodriguez

14:57 22 Dec '05

its totally possible - we've even implemented it a few times - that is in 1.1 - however - i would seriously think twice about doing it in 1.1 wait until the master pages come out so that you dont have to rewrite most of your pages later Danny! http://www.animusoft.com/_sections/about/default.aspx
Sign In·View Thread·PermaLink

when FrameworkInitialize is called?

Pawel Rogozinski

2:17 2 Jan '05

Hi, do you have any idea when and by what means is FrameworkInitialize method called? I wonder how this method is called, because when i try to create a new instance of webform1_aspx class i got null reference exceptions, that mean, the tree of controls was not properly build. When i move frameworkinitialize's code into constructor, everything works fine. anyone knows why? Pawel Rogozinski
Sign In·View Thread·PermaLink

Re: when FrameworkInitialize is called?

msexpert

4:04 2 Jan '05

Hi,

FrameworkInitialize is actually one of the first Page methods that get called by ASP.NET pipe line. ASP.NET call Page ProcessRequest method that first of all calls FrameworkInitialize. so actually is the first function that really get called (actually FrameworkInitialize is being called before page Init and Load get called). that's not surprising due to the fact that FrameworkInitialize actually build all page controls that had been declered by user as XML declerations (ASPX file).

HTH

Natty

5.00/5 (1 vote)

Nice Article !!!

20:05 2 Mar '04

Thank you for sharing your knowledge. UB You may stop this individual, but you can't stop us all... after all, we're all alike. +++Mentor+++
Sign In·View Thread·PermaLink

Constructor

Joe Sadowski

4:46 30 Jan '04

Great article, really shows the inner workings of the aspx compilation process. The one problem is the constructors are not executed in the order that was shown at the bottom of the article. Constructors in the .net world are called from the class highest up the inheritence chain (always System.Object) to the lowest. So, in this case we will actualy see the code for the WebForm1 constructor execute before the code for the adbdef constructor.


using System;

// Demonstrates the execution order of constructors in inherited classes

namespace ConstructorTest
{

	class StartUp
	{
		static void Main()
		{
			// Create a new instance of SubClass to show the order the constructors are called
			new SubClass();
		}
	}

	public class BaseClass
	{
		public BaseClass()
		{
			// Executed before the constructors for any class that inherits from this is executed
			Console.WriteLine( "BaseClass Constructor Called." );
		}
	}

	public class SubClass : BaseClass
	{
		public SubClass()
		{
			// Executed after the constructor for the BaseClass class is called
			Console.WriteLine( "SubClass Constructor Called." );
		}
	}

}

Re: Constructor

Natty Gur

5:07 30 Jan '04

Sharp Eye, you are absolutely right. I probably mixed them up. I'll change that mistake. Thanks!!!
Sign In·View Thread·PermaLink

great

Prashant Agrawal

21:19 22 Jan '04

ya its a great article.

i have one question in my mind : As .NET creatind the single DLL for all the *.cs file in the win.. dir so can it not be possible that we can use that dll(one dll generated for all the *.cs) in our new .net application and load the page that we are loading by using the old .net application (refering that dll in our new asp application) . if yes then please tell me how you will do. that

thanks

Prashant

Interesting...

Kant

7:02 20 Jan '04

Thanks for sharing the info. The article needs some polish related to fonts/tags. Promise only what you can do. And then deliver more than what you promised. This signature was created by "Code Project Quoter".
Sign In·View Thread·PermaLink	5.00/5 (1 vote)

Last Visit: Monday, December 1, 2008 10:49 PM Last Update:Monday, December 1, 2008 10:49 PM

General News Question Answer Joke Rant Admin