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New Code Compilation Features in ASP.NET Whidbey

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Setup Instructions
Build an XML Web Service
Microsoft Visual Studio .NET Guided Tour
Building a Rich Windows Form
New Code Compilation Features in ASP.NET Whidbey
Authoring ASP.NET Server Control Adapters - An Introduction
Experience the Extensibility of Windows Forms
Building a mobile Web Form
XML Web Services at Work
Building a Web Form and Test for Scalability

New Code Compilation Features in ASP.NET Whidbey

G. Andrew Duthie
Graymad Enterprises, Inc.

October 2003

Summary: Examines how ASP.NET 'Whidbey' makes working with code even easier than before. The Code directory automatically compiles code for your site, while precompilation can make deployment easier than ever before. (14 printed pages)

Download the source code for this article.


The New Code-Behind Model
Code Directory
Interest Calculator
Precompilation Support
In-Place Precompilation
Precompilation for Deployment
IntelliSense Everywhere!


The upcoming release of Microsoft® ASP.NET, code name ASP.NET 'Whidbey' (after the code name for the upcoming release of Microsoft® Visual Studio® .NET) introduces a basket load of new features (and changes to existing features). Some of these take advantage of new features in the underlying Microsoft® .NET Framework version on which ASP.NET Whidbey is built. One of the most useful set of features relates to how your code is compiled.

In this article, we'll look at the major changes in the compilation model for ASP.NET Whidbey, describe how these changes will affect how you write your ASP.NET applications, and see how to use them.

The changes and new compilation features break down into four basic areas:

1.                  Changes to the code-behind model.

2.                  The new code directory.

3.                  Added support for pre-compiling ASP.NET applications.

4.                  Microsoft® IntelliSense® enhancements.

The New Code-Behind Model

By default, sites developed using Visual Studio .NET 2002 or 2003 use a feature called code behind to separate visual elements (HTML markup, controls, and so on) from UI-related programming logic. When a developer created a new Web Form (such as foo.aspx), Visual Studio would automatically create an associated Codebehind class file with the same name as the Web Form, along with an appended .vb or .cs, depending on the language used for the project. The class file would be associated with the Web Form by the Codebehind and Inherits attributes of the @ Page directive.

This class file contained event-handling code, including code to wire up the event handlers to the proper events, as well as separate declarations for each control added to the .aspx file in the Visual Studio Web Form editor. When the Web application project is compiled (built), all of the Codebehind classes in the project are compiled into a single .NET assembly, which is placed in the application's bin directory. The Web Forms pages themselves are compiled dynamically at run time, and each Web Form inherits from the Codebehind class associated with it. See the MSDN Library article, Web Forms Code Model, for more information on the code-behind model in Visual Studio .NET 2003 and ASP.NET 1.1.

While the original code-behind model is nice in theory (who doesn't want to separate programmatic logic from UI elements?), it has several drawbacks:

·                     Required rebuilds. The Codebehind class is not automatically compiled at runtime in Visual Studio .NET, so any change to a Codebehind class requires the entire project to be rebuilt in order to pick up the changes. (Note that you can specify that a code-behind file is to be compiled dynamically using the src attribute of the
@ Page directive, but this is not the default in Visual Studio .NET.)

·                     Shared development issues. All Codebehind classes in a project compile to a single assembly, so it is more difficult to have multiple developers working on a project without bottlenecks.

·                     Brittle code. Controls exist both declaratively (in the .aspx page) and programmatically (in the Codebehind class), and it's easy for code to break if the two sets of controls are not kept in sync properly.

·                     Added complexity and lack of single-file support. Visual Studio .NET requires the use of code behind for many of its productivity-enhancing features, including IntelliSense statement completion. Unfortunately, these features often add a large amount of relatively complex code to the Codebehind class, adding to the problem of 'brittle' code, since changes to the code injected by Visual Studio .NET can too easily break the page.

With these drawbacks in mind, the team responsible for ASP.NET and Visual Studio .NET Whidbey decided to re-think the code-behind model. The new code-behind model takes advantage of a new feature of Microsoft® Visual Basic® .NET and C# called partial classes (partial types in C#). Partial classes allow you to define different parts of a class in more than one file. At compile time, these parts are combined by the compiler. ASP.NET Whidbey uses the new CompileWith and Classname attributes of the @ Page directive to identify the Codebehind partial class to combine with the .aspx page. By taking advantage of partial classes and making other changes, the ASP.NET team was able to do the following:

·                     Remove the need for control declarations and event wire-up code in Codebehind classes (events are wired up declaratively in the control declaration).

·                     Allow both Web Forms pages and Codebehind classes to be compiled dynamically at run time, eliminating the need to rebuild an entire project for a single change.

·                     Reduce file contention in shared development.

·                     Provide the same IDE experience for both developers choosing to work with code-behind files, as well as those who prefer single-file development (all code and markup in the .aspx file).

Here's a before/after view of the changes in the code-behind model. The following code is simply the default code created by Visual Studio when you add a new Web Form using code behind (referred to as Web Form with code separation in Visual Studio .NET Whidbey):

Visual Studio .NET 2002/2003


<%@ Page Language='vb' AutoEventWireup='false'

  Codebehind='WebForm1.aspx.vb' Inherits='TestWebApp_121602.WebForm1'%>

<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.0 Transitional//EN'>




    <meta name='GENERATOR' content='Microsoft Visual Studio .NET 7.1'>

    <meta name='CODE_LANGUAGE' content='Visual Basic .NET 7.1'>

    <meta name=vs_defaultClientScript content='JavaScript'>

    <meta name=vs_targetSchema



  <body MS_POSITIONING='GridLayout'>    <form id='Form1' method='post' runat='server'>





Public Class WebForm1

    Inherits System.Web.UI.Page

#Region ' Web Form Designer Generated Code '

    'This call is required by the Web Form Designer.

    <System.Diagnostics.DebuggerStepThrough()> _

    Private Sub InitializeComponent()

    End Sub

    'NOTE: The following placeholder declaration is

    'required by the Web Form Designer.

    'Do not delete or move it.

    Private designerPlaceholderDeclaration As System.Object

    Private Sub Page_Init(ByVal sender As System.Object, _

        ByVal e As System.EventArgs) Handles MyBase.Init

        'CODEGEN: This method call is required by the Web Form Designer

        'Do not modify it using the code editor.


    End Sub

#End Region

    Private Sub Page_Load(ByVal sender As System.Object, _

        ByVal e As System.EventArgs) Handles MyBase.Load

        'Put user code to initialize the page here

    End Sub

End Class

Visual Studio .NET Whidbey


<%@ page language='VB' compilewith='Default.aspx.vb'

  classname='ASP.Default_aspx' %>


<head runat='server'>

    <title>Untitled Page</title>



    <form runat='server'>





Imports Microsoft.VisualBasic

Namespace ASP

Expands Class Default_aspx

End Class

End Namespace

As should be fairly clear from the foregoing examples, the code produced by Visual Studio .NET Whidbey is far cleaner and easier to read. And you don't have to sacrifice drag-and-drop functionality or IntelliSense to get it.

Code Directory

Another cool and useful new feature in ASP.NET Whidbey is the addition of the Code directory. The Code directory, like the bin directory, is a special directory used by ASP.NET, but with a twist: While the bin directory is designed for storing pre-compiled assemblies used by your application, the Code directory is designed for storing class files to be compiled dynamically at run time. This allows you to store classes for business logic components, data access components, and so on in a single location in your application, and use them from any page. Because the classes are compiled dynamically at run time and are automatically referenced by the application containing the Code directory, you don't need to build the project before deploying it, nor do you need to explicitly add a reference to the class, and you can easily make changes to a component and deploy with a simple XCOPY or with a drag-and-drop operation. In addition to simplifying the deployment and referencing of components, the Code directory also greatly simplifies the creation and accessing of resource files (.resx) used in localization, as well as automatically generating and compiling proxy classes for WSDL files (.wsdl).

To better illustrate how this works, let's take a look at a couple of examples. In the first example, we'll see how to create a simple business component and access it from a Web Forms page.

Interest Calculator

First, we open Visual Studio .NET Whidbey, and create a new Web site called Compilation. Once the Web site has been created, the IDE should look similar to Figure 1.

Figure 1. Visual Studio .NET Whidbey Web site

Next, we'll add the Code folder to the Web site by right-clicking the project, and selecting New Folder. The folder must be named Code, but the name is not case sensitive. Once we've added the folder, we can add a new class file by right-clicking the Code folder and clicking Add New Item, and then choosing the Class item in the Templates pane of the Add New Item dialog box. We'll name the class CalculateInterest.vb. We then add the code that calculates the interest (the code goes between the Class and End Class statements):

Public Function CalcBalance(ByVal Prncpl As Integer, _

                        ByVal Rate As Double, _

                        ByVal Years As Integer, _

                        ByVal Period As Integer) As String

    Dim BaseNum As Double = (1 + Rate / Period)

    CalcBalance = _

        Format(Prncpl * System.Math.Pow(BaseNum, _

        (Years * Period)), '#,###,##0.00').ToString

End Function

Once the component class is complete, we need to modify the Default.aspx page to provide the necessary fields for entering data, and to call the component's CalcBalance method. For the sake of simplicity, the full listing for Default.aspx is shown below (note that Default.aspx uses the single-file code model).


<%@ page language='VB' %>

<script runat='server'>   

    Sub Button1_Click(ByVal sender As Object, _

        ByVal e As System.EventArgs)

        Dim Calc As New CalculateInterest

        Label6.Text = '$' & _

            Calc.CalcBalance(Convert.ToInt32(TextBox1.Text), _

                (Convert.ToInt32(TextBox2.Text) / 100), _

                Convert.ToInt32(TextBox3.Text), _


        Label6.Visible = True

    End Sub



<head runat='server'>

    <title> Interest Calculator</title>



    <form runat='server'>

        <asp:label id='Label1'

            runat='server'>Principal ($):</asp:label>

        <asp:textbox id='TextBox1' runat='server'>


        <br />

        <asp:label id='Label2'

            runat='server'>Interest Rate (%):</asp:label>

        <asp:textbox id='TextBox2' runat='server'>


        <br />

        <asp:label id='Label3' runat='server'>Years:</asp:label>

        <asp:textbox id='TextBox3' runat='server'>


        <br />

        <asp:label id='Label4'

            runat='server'>Compounding Frequency:</asp:label>

        <asp:dropdownlist id='Dropdownlist1' runat='server'>

            <asp:ListItem Value='1'>Annually</asp:ListItem>

            <asp:ListItem Value='4'>Quarterly</asp:ListItem>

            <asp:ListItem Value='12'>Monthly</asp:ListItem>

            <asp:ListItem Value='365'>Daily</asp:ListItem>


        <br />

        <asp:label id='Label5'

            runat='server'>Ending Balance: </asp:label>

        <asp:label id='Label6'

            visible='false' runat='server'></asp:label>

        <br />

        <asp:button id='Button1'

            runat='server' text='Calculate' onclick='Button1_Click' />




In design view, the modified Default.aspx should look similar to Figure 2.

Figure 2. Default.aspx in design view

One important thing to note is that as you type the code in the <script> block that calls the component class, you will get full IntelliSense statement completion, including on the component class, as shown in Figure 3. This is a significant improvement over Visual Studio .NET 2003, which provides no support for IntelliSense in server-side <script> blocks.

Figure 3. IntelliSense in Source view

Browsing Default.aspx results in the output shown in Figure 4. Fill in some values for principal, rate, and years and click Calculate, and the output should look similar to Figure 5.

Figure 4. Initial output of Default.aspx

Figure 5. Output after calculation

Resource Files

If you've ever worked with Web applications in Visual Studio .NET 2002 or 2003, you've no doubt noticed that every time you created a new Web Forms page, in addition to the .aspx page itself and the .vb or .cs code-behind file, Visual Studio also created a matching file with the .resx extension (that is, WebForm1.aspx.resx). Now if you're like most Web developers, you either ignored or attempted to get rid of these files, since it wasn't very intuitive what they were, and/or how to use them. Well, the short answer is that .resx files are resource files, and they are used primarily for storing multiple versions of resources, such as text strings in different languages for localization.

In Visual Studio .NET 2002 and 2003, resource files needed to be added to the project assembly as part of the process of building the project, and required importing two namespaces, creating a ResourceManager object, and calling its GetString method just to access a resource string.

Thanks to the Code directory, the process of accessing resources is far simpler in Visual Studio .NET Whidbey, as we'll see in the following example.

We'll get started by creating the resource file, using the same project as in our previous example. First, right-click the Compilation Web site created earlier, and click Add New Item In the Add New Item dialog box, select the Assembly Resource File template, name the file strings.resx, and click Open. The default view of strings.resx should look similar to Figure 6.

Figure 6. Editing a resource file in the XML editor

Add the following items to the data table (you can leave the comment, type, and mimetype columns blank):




Please choose a color:


You chose Red!


You chose Green!


You chose Blue!

Now repeat the process to add a new resource file named strings.en-GB.resx, and add the following item to its data table and save the file (because we did not add entries for txtColorResponse*, the values for these items from strings.resx will be used for all clients):




Please choose a color:

Now, in order to take advantage of the magic of the Code directory, we'll need to drag both of the .resx files into the Code directory from the root of the Web site. Once that's done, the result will look like Figure 7.

Figure 7. .resx files in the Code directory

To demonstrate how easy it is to now use the resource files we created, we'll add a Web Form to the project by right-clicking the Web site node, and clicking Add New Item. In the Add New Item dialog box, we select Web Form, name the page ColorPicker.aspx, and click Open. Modify the page so that it matches the listing below.


<%@ page UICulture='en-GB' language='VB' %>

<script runat='server'>


    Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)

        Label1.Text = Resources.strings.txtColorPrompt

    End Sub


    Sub Submit_Click(ByVal sender As Object, _

        ByVal e As System.EventArgs)

        Label1.ForeColor = _


        Select Case Dropdownlist1.SelectedValue

            Case 'Red'

                Label1.Text = Resources.strings.txtColorResponseRed

            Case 'Green'

                Label1.Text = Resources.strings.txtColorResponseGreen

            Case 'Blue'

                Label1.Text = Resources.strings.txtColorResponseBlue

        End Select

        Dropdownlist1.Visible = False

        Submit.Visible = False

    End Sub



<head runat='server'>

    <title>Color Picker</title>



    <form runat='server'>

        <asp:label id='Label1' runat='server'>Label</asp:label>

        <asp:dropdownlist id='Dropdownlist1' runat='server'>

            <asp:listitem value='Red'>Red</asp:listitem>

            <asp:listitem value='Green'>Green</asp:listitem>

            <asp:listitem value='Blue'>Blue</asp:listitem>


        <asp:button id='Submit'

            text='Submit' runat='Server' onclick='Submit_Click' />




When we browse ColorPicker.aspx from a browser, the default output will appear similar to Figure 8. If someone browsing from a system set up for the United Kingdom browses the page (you can simulate this by setting the UICulture property of the page to 'en-GB' and saving the page), the output will appear as shown in Figure 9 (note that we've added the u in 'colour').

Figure 8. Default output of ColorPicker.aspx

Figure 9. Output of ColorPicker.aspx for UK systems

Note that accessing resource files in ASP.NET Whidbey requires only a single line of code. Because the resource file is embedded and referenced automatically by placing it in the Code directory, we do not need to reference any namespaces or assemblies, nor do we need to create objects in order to access the resource strings. And ASP.NET also takes care of determining which resource file should be used, based on the settings of the user's browser—so we don't have to try to figure that out at run time and respond appropriately. It just works.

Precompilation Support

One of the advantages of ASP.NET Web Forms is that because of dynamic compilation, you can easily make changes to an .aspx page, save the page, and the page is updated, without the need for a recompile (as long as you're not using code behind). But dynamic compilation isn't appropriate for every application, and it carries with it an initial performance hit when the application is accessed for the first time. Additionally, there may be times when you'd really like to deploy an application without the source code.

If one of those situations applies to you, you'll be glad to hear that ASP.NET Whidbey will ship with support for precompiling Web sites. ASP.NET Whidbey supports two modes of pre-compilation: in-place precompilation, and precompilation for deployment.

In-Place Precompilation

In-place precompilation allows you to manually cause all the pages in your Web site to be batch compiled. This is essentially what happens the first time a user hits a page within your application, except that in the latter case, the user gets to sit and wait while the batch compilation takes place.

There are two main reasons to use in-place precompilation: first, it eliminates the performance hit of batch compiling on the first page request, and second, it allows you to find compilation errors before your users do.

In-place precompilation is also easy to do. Simply browse to the root of your Web site, plus the special handler name precompile.axd (those familiar with ASP.NET's Trace feature will note the similarity to the trace.axd handler name):


where mywebsitename is the name of your Web site. After precompiling your site, requests for pages within the site should be fulfilled immediately, without any compilation lag.

Precompilation for Deployment

The second precompilation mode allows you to create an executable version of your entire Web site that can be deployed without any source code, including HTML and other static files. As such, precompiling for deployment can prevent easy access to the intellectual property represented by your code. The resulting set of assemblies and stub files can be deployed to a production server through XCOPY, FTP, Windows Explorer, and so on.

To precompile a site for deployment, ASP.NET Whidbey provides a command-line utility called aspnet_compiler.exe. To invoke the ASP.NET precompiler on a file system Web site, you would open a command window, navigate to the location of the .NET Framework, install (<windows>Microsoft.NETFramework<version>), and enter the following command:

aspnet_compiler /v /<websitename> –p <source> <destination>

where <websitename> is the name of the Web site (as you'd enter it in a browser), and <source> and <destination> are file system paths pointing to the location of the site to compile and the location to which the compiled version should be output. For our example Web site, the command would look something like the following (note that the following is a single command):

aspnet_compiler /v /Compilation

–p c:WebSitesCompilation c:WebSitesCompilation_Compiled

If you want to view all of the available options for the ASP.NET precompiler, you can simply enter the command:

aspnet_compiler /?

Note that some of the command-line options require your Web site to be a valid Microsoft® Internet Information Services (IIS) application in order to work correctly.

If you navigate to the destination directory in Microsoft® Windows Explorer, you'll see that the result of precompiling a Web site is a site with a bin directory containing several assemblies and descriptive files, as well as a number of stub files with the same names as the original pages, but with the code (both HTML and executable code) stripped out. If you browse the site, the output will be identical to the original site. Note that you cannot use in-place precompilation on a site that has been precompiled for deployment, for the obvious reason that it has already been precompiled.

IntelliSense Everywhere!

One of my biggest gripes (and one that I'm sure is shared by many developers) about Visual Studio .NET 2002 and 2003 is the inconsistent support for IntelliSense and other productivity-enhancing features. Want to drag a control from the toolbox onto the page in HTML view? Nope, can't do it. In fact, the Web Forms panel of the toolbox isn't even available when you're in HTML view! Want to write your code inline in your .aspx pages instead of using code behind? Well, you can do that, but you have to give up IntelliSense, drag-and-drop functionality, and more to do it. Finally, as I illustrated in a recent article on the MSDN ASP.NET Developer Center, getting design-time support for custom controls in Visual Studio .NET 2002 or 2003 requires jumping through a number of hoops, including a somewhat inelegant (though effective) XSL hack.

The good news is that thanks to the unification of the compilation model in ASP.NET Whidbey, all of this goes away. In Visual Studio .NET Whidbey, you will be able to write your code inline, or using the new code-behind model, and get the same support for dragging controls, for IntelliSense statement completion, and for all those productivity enhancements you wanted to use, but were prevented from doing so because of the way you like to code. Additionally, design-time support for both custom server controls and Web controls is much improved, including the addition of IntelliSense statement completion for your custom controls in Source view (the Visual Studio .NET Whidbey equivalent of HTML view).


The changes to the compilation model within ASP.NET Whidbey, and the accompanying feature improvements of Visual Studio .NET Whidbey, represent a great leap forward for providing developers with the flexibility that they crave, while still allowing them to take full advantage of the productivity features provided by the IDE. The greatly simplified code-behind model will help to make that feature more useful and less onerous, while the addition of full support for inline code will definitely please those developers who prefer all of their code in a single .aspx file.

The Code directory promises to be a big productivity enhancer, particularly for those working on small to medium projects that change rapidly, and anyone for whom a complicated build process really gets in the way of getting things done. It also provides a much more straightforward and simple means of accessing business logic components, resource files, WSDL files, and other resources, by automatically compiling, embedding, or creating proxies for these resources, and automatically referencing them, allowing them to be accessed with very little code.

The precompilation features make it easy for developers to improve the startup performance of their sites, and when desired, to add a measure of protection to their valuable intellectual property by shipping fully-functional Web applications without source code or HTML.

Finally, the combination of all of these features means that developers can look forward to a much richer experience in Visual Studio .NET Whidbey, with full IntelliSense support in both inline and code-behind models, and for all views of a given page, without having to constrain their development to a single style mandated by the tool.

About the Author

G. Andrew Duthie is the founder and principal of Graymad Enterprises, Inc., providing training and consulting in Microsoft Web development technologies. Andrew has been developing multitier Web applications since the introduction of Active Server Pages. He has written numerous books on ASP.NET, including Microsoft ASP.NET Programming with Microsoft Visual Basic, Microsoft ASP.NET Programming with Microsoft Visual C#, and ASP.NET in a Nutshell (second edition). Andrew is a frequent speaker at events, including Software Development, the Dev-Connections family of conferences, Microsoft Developer Days, and VSLive! He also speaks at .NET user groups as a member of the International .NET Association (INETA) Speaker's Bureau. You can find out more about Andrew at his company's Web site,



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