Target the .NET Compact Framework using Visual Studio Express
Microsoft only supports Visual Studio Professional for developing Windows Mobile applications and, more generally, code based on the .NET Compact Framework. You get nice things like application deployment and emulators and remote debugging and all. But if you just want to compile something against the .NET Compact Framework, for example to check that you’re using supported methods and classes, you can do that with Visual Studio Express.
Create a project in Visual Studio Express and open it in a text editor.