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Understanding XAP File In Silverlight

Xap files are created when you compile a silverlight application. Before you work on silverlight applications you should know some important details about this file like what Xap file is and what it contains. In this tutorial I will answer these questions.

New Project

First of all create a new project by selecting Silverlight application from Visual Studio Installed templates

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Enter the project name, select the location and click ok. When you click Ok a popup window asks you whether you want to host the silverlight application on website or not.

Picture showing selecting the silverlight version of the project

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Click ok and a new project will be created. Check the solution explorer there are two projects, one is the silverlight application and other is the web based project on which application is hosted.

Picture showing the ClientBin folder inside the silverlight project

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Check the highlighted ClientBin folder. This folder contains xap file. But as the solution is not compiled there is no xap file created.

Right click on the solution in solution explorer and click on Build Solution. Once the build gets succeeeded you can see the xap file in ClientBin folder.

Picture showing the xap file inside the ClientBin folder

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To check the xap file right click on the ClientBin folder and click on "Open Folder in windows explorer" option. You will see the xap file with the same name as that of silverlight application.

Now change the extension of the file from .xap to .zip.

Picture showing changing the file extension of xap file to zip

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Double click on the zip file to see the contents of the file with .zip extension(make sure you have winzip installed on your machine).

Picture showing the different files inside the xap file

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There are two files AppManifest.xml and MyFirstApplication.dll. The MyFirstApplication.dll is the compiled version of your silverlight application and the name of dll is same as the name of your silverlight application. The .xap file(which is renamed to .zip file) may contains some supporting assemblies as well if your silverlight application is using any.

The another xml file AppManifest.xml contains the information about the assemblies and the silverlight application. Open the xml file in any editor.

Picture showing the contents of the AssemblyManifest.xml file

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The xml file start with Deployment tag. Check the attributes EntryPointAssembly, EntryPointType and RuntimeVersion.

EntryPointAssembly – This attribute defines the name of the main assembly i.e. the assembly contains the compiled silverlight application.

EntryPointType – This attribute specifies the name of the class that the main assembly contains.

RuntimeVersion – The version on which the silverlight application is built.

In the Depoyment.Parts there is a child tag AssemblyParts which contains the assembly information. It should be noted that if a .xap file contains some supporting assemblies then the information about the assemblies comes in Deployment.Parts section like

<Deployment.Parts>
	<AssemblyPart x:Name="Assembly1" Source=" Assembly1.dll" />
	<AssemblyPart x:Name="Assembly2" Source=" Assembly2.dll" />
	<AssemblyPart x:Name="Assembly3" Source=" Assembly3.dll" />
</Deployment.Parts>

Posted By -	karan Gupta

Posted On -	Wednesday, December 28, 2011

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