How are the XAP files structured?

Question

Questions:

1. Are XAP files self-contained?
2. Do they link in all DLLs I have referenced in the project?
3. If I need to distribute my app, is all I have to do is hand someone the XAP file?

Answer 1

Silverlight XAP files can be tricky if you're using anything other the the core silverlight assemblies (eg. SilverlightToolkit).

1. XAP files are just zip files - open one up and take a look. They are self contained to the extent that any custom/extra dlls are included - the standard Silverlight assemblies will be installed when a user installs Silverlight.

2. References to dlls are required in the .proj files for every assembly that will be used. Ie. unlike other project types, if one project references another project, both projects need to reference all dlls used by either project.

3. You should be able to just hand someone the XAP file if you want - but Silverlight was designed to be used in browsers, so you will need to include the generated test page at least. The best, and most useful, is to provide a publicly accessible web page that hosts your silverlight app.

HTH.

Answer 2

1. By default, yes. For alternatives, see answer 3.
2. By default, all except the core DLLs installed by the runtime; it will contain anything from the SDK, Toolkit, 3rd party controls, or your own libraries.
3. By default, yes. However, there is an option as of Silverlight 3 to package certain assemblies (for example anything from the SDK) into separate ZIP files, which are downloaded separately. In Visual Studio, look in the project properties for a checkbox called "Reduce XAP size by using application library caching." This option toggles whether to create/use the ZIP files or not. Enabling the ZIP option allows multiple Silverlight apps to share the dependency on the ZIP files, so that instead of packaging everything into the XAP every time, you just download the ZIP for one app, and it's saved in the browser cache for other apps.

As for the general contents of the XAP file, there are 2 important bits:

1. Foo.dll - your project's main assembly (renamed as appropriate)
2. AppManifest.xaml - describes the requirements for you app, e.g minimum runtime version required, the entry point into Foo.dll, and other settings, including Out-of-browser settings, or whether to use the Library caching feature mentioned above.

Anything else is just content used by your app.

Answer 3

Even though this question is already answered, i'm going to throw this one in too because it hasn't been mentioned yet.

You mention that you are using SL4 - if you are running out of browser (OOB) then you can just ship the XAP file, and use sllauncher.exe (2) to "install" it to the client machine. As part of that install you can also specify where updates are to be sourced from, which is important for when you find bugs or the requirements change.