Next we need to tell the project what languages are supported. Visual Studio doesn’t currently expose this part of the project information, but we can easily edit it. Make sure you save all changes so any changes to the .csproj file are saved to disk before we edit the file. Next go to the project’s folder on the disk drive by right clicking on the project and selecting “Open folder in Windows Explorer”. Select the .csproj file for your application (be careful not to select the .csproj.user file) and open it with Notepad or your favorite text editor.
Look for the <SupportedCultures></SupportedCultures> element and add the culture codes of the cultures you wish to support separating each culture with a semicolon. This list should not include the neutral language of the assembly. See http://msdn.microsoft.com/en-us/library/hh202918(v=VS.92).aspx for a list of cultures supported by various versions of Windows Phone. For the purposes of this example, we’ll be supporting Spanish, simplified Chinese and French in addition to the default culture of English (United States) so our SupportedCultures node looks like:
After making your changes, save the .csproj file and go back to Visual Studio. Click reload when Visual Studio prompts you that the project has changed so the changes to the project file can take effect.