XAP (pronounced ZAP) is the file extension for a Silverlight-based application package (.xap). This file contains the compressed assemblies and resources of a Silverlight 2 application.

A .xap file is a Silverlight-based application package (.xap) that is generated when the Silverlight project is built.

Tools, such as Visual Studio 2008 with the Microsoft Silverlight Tools Beta 2 for Visual Studio 2008, allow you to create Silverlight applications that are heavily client based using managed code. You can use managed code, such as C# or Visual Basic, and benefit by using the tools that you are used to working with. 

Once you have created the .xap file (explained below), the Silverlight 2 plug-in downloads the file and runs it in a separate work space.

A .xap file is used to contain and transfer the assemblies and resources of a managed code application. This managed code application must be run within the Silverlight 2 browser plug-in.

http://www.microsoft.com/silverlight/resources/install.aspx?v=2.0

Compatible Operating Systems and Browsers

To view the contents of a .xap file you can rename the extension of the .xap file to .zip. Then view the .zip file using any standard .zip utility.

A basic xap file will have an assembly related to specific code for the application, an application manifest file and any additional assemblies need to run the application. At a minimum, two files are needed, the application manifest file and the application assembly.

For example:

AppManifest.xaml

MyPianoV2.dll

The AppManifest.xaml file contains the deployment details needed to run the application.

Basic example:

For more information, see Katrien De Graeve blog post titled Silverlight 2: structure of the new .XAP file (Silverlight packaged application).

You can use any dll inspection utility. Here’s an example of the contents of myPianoV2.dll:

 

·         Visual Studio 2008 using the Microsoft Silverlight Tools Beta 2 for Visual Studio 2008.

·         Expression Blend 2.5 June 2008 Preview

·         Chiron.exe – Located in the Tools folder of your Silverlight Tools Beta 2 for Visual Studio 2008 installation. For more information see, Dynamic Languages in Silverlight 2.

Check the following:

·         Make sure you are using the Silverlight 2 Beta 2 plug-in.

·         Make sure you have the XAP mime type set for IIS (see below).

·         Check to be sure you included your resources, such as graphics, with your Silverlight Application (see below).

·         Make sure the .xap file is contained in the ClientBin folder of your Web application.

·         Check the Silverlight Tools page for additional troubleshooting details.

The .xap mime type is:

For more information, see Michael Schwarz blog post and Microsoft Help and Support.

1.       Install the following:

·         Visual Studio 2008.

·         The .NET Framework version 3.5.

·         Microsoft Silverlight Tools Beta 2 for Visual Studio 2008.

·         Silverlight version 2 Beta 2 plug-in.

2.       Follow the steps in the following walkthrough to create a .xap file:
Walkthrough: Integrating XAML into an ASP.NET Web Site Using Managed Code

C#, Visual Basic

IronPython, IronRuby, and Managed JScript

For more information, see Programming Silverlight with Dynamic Languages and Dynamic Languages in Silverlight 2.

You can use the ASP.NET Silverlight Server Control to reference your .xap file. Specifically, you use the Source property to reference the XAP application package. The Version must be set as well.

Code contained in an .aspx file:

Yes.

Code (C# & VB) that shows how to include a .xap file in a Web page.

Example that shows a running Silverlight 2 Beta 2 application. Note: You will need to install the current runtime plug-in, unless you already have it installed. After installing, close all browser windows and click the Example link.

The example above shows one way to include resources in a Silverlight 2 application. However, Katrien De Graeve has a blog entry titled Different ways for loading images and files in Silverlight 2 applications that explains how to include resources in more detail.

The XmlXapResolver class is used to resolve resources that are contained in the Silverlight application’s XAP package.

This file type is not related to Silverlight.

The Xbox Audio Creation Tool Project File format (.xap), is read and written by the XACT authoring tool (xact.exe), is utilized by the command-line build environment (xactbld.exe), and contains all of the instructions necessary to generate XACT content. It is a complete description of all XACT wave banks, sound banks, and global settings. For more information see, XACT Project File Format (.xap).

Yes. Here are a number of links that you may find interesting and helpful.

ASP.NET Controls for Silverlight – ASP.NET Documentation that includes code and running examples.

System.Web.UI.SilverlightControls Namespace – ASP.NET Documentation - managed reference.

Sys.UI.Silverlight (client) Namespace – ASP.NET Documentation – client reference

Silverlight FAQ

Why Silverlight?

Silverlight Resources

Silverlight 2 Beta 2 and Silverlight Streaming

Scott Guthrie’s - Silverlight 2 Beta2 Released

 Thanks

Cool stuff Here is some useful link also

 Silver Light

Moss 2007 FAQS and Articles

Thanks

Mani 

Hi ,

http://www.encyclo.co.uk/define/XAP 

U r Information is good.

Thanks for the info.

Vissu

Good one for beginers: http://silverlight.net/GetStarted/

This file type XACT not related to Silverlight.

The Xbox Audio Creation Tool Project File format (.xap), is read and written by the XACT authoring tool (xact.exe), is utilized by the command-line build environment (xactbld.exe), and contains all of the instructions necessary to generate XACT content. It is a complete description of all XACT wave banks, sound banks, and global settings. For more information see, XACT Project File Format (.xap).

 Here are a number of links that you may find interesting and helpful.

ASP.NET Controls for Silverlight – ASP.NET Documentation that includes code and running examples.

System.Web.UI.SilverlightControls Namespace – ASP.NET Documentation - managed reference.

Sys.UI.Silverlight (client) Namespace – ASP.NET Documentation – client reference

Silverlight FAQ

The link "Walkthrough: Integrating XAML into an ASP.NET Web Site Using Managed Code" is broken in your post.

Regards,

Kasimier

I have tried this 

 xmlns:datavis="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit">

with the Nov 09 Silver light Toolkit.

But i keep grtting error on : <datavis:StylePalette>
The tag 'StylePalette' does not exist in XML namespace 'clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit

Any ideas...