Kévin Gosse

[WP7] Inject a file in a xap using post-build event

Let’s say that your application is dynamically loading resources, and you have to constantly add/remove new resources during the development. In this scenario, it could be a huge-time saver to just tell Visual Studio to take the contents of a folder and inject it into your application. I don’t think there’s an out-of-the-box way to do that, but you can inject the files yourself using a post-build event.

How? The output of every WP7 project is a .xap file, which is just a zip file with a different extension. So you can edit it using whichever zip extractor you like. In our case, let’s use 7zip.

First, create a basic application, and put an image control in the xaml:

   1: <Grid x:Name="ContentPanel"

   2:       Grid.Row="1"

   3:       Margin="12,0,12,0">

   4:     <Image x:Name="Image"

   5:            Width="300"

   6:            Height="300"

   7:            Source="Someimage.png" />

   8: </Grid>

Make sure that the ‘someimage.png’ file does not exist in your project. Compile, run, and surely enough nothing is displayed.

Now, add the following line to the post-build event of your project: (right-click on the project, properties, “Build Events”)

   1: "C:\Program Files (x86)\7-Zip\7z.exe" a -tzip $(ProjectDir)$(OutDir)Test.xap E:\someimage.png

• "C:\Program Files (x86)\7-Zip\7z.exe" is self explanatory: this is the path where you installed 7zip

• the “a” switch tells 7zip to add a file to the archive

• the “-tzip” switch forces the archive format to zip

• “$(ProjectDir)$(OutDir)” is automatically replaced by the output path of your project

• “Test.xap” is the name of the generated xap. Change it with the name of the file generated by your project

• “E:\someimage.png” is the path of the file(s) to inject

Rebuild the solution (to force Visual Studio to re-deploy the xap), then run the application, and your ‘someimage.png’ image should be displayed, even though it never had been added to the Visual Studio solution.

Hope that helps!