How to write a class library that will work on .NET 3.5 compact framework AND regular framework?

Question

How do I write a .NET class library that I can recompile for either the regular .NET 3.5 Framework, or the .NET 3.5 Compact Framework?

Answer 1

The two frameworks aren't binary compatible*, unfortunately, but don't let that stop you.

Create two projects in your solution (one normal Class Library project, and one Compact Framework Class Library project), and add all the files from one project to the other as links by clicking "Add|Existing File" and then checking the "add as link" checkbox on the file dialog.

Now you only have one set of source code to maintain, but your solution will build both DLLs at the same time.

If you have any code inside a file that's specific to the desktop framework and won't work on the compact framework, you can wrap it in a compiler directive (at least in C#) like this:

#if PocketPC
    // mobile-specific stuff here
#else
    // desktop-specific stuff here
#endif

• Note that although you can't use desktop-framework binaries on a mobile platform, the opposite is not true. Compact framework executables can run on the desktop. I'm fairly certain, however, that a desktop application cannot reference a compact framework assembly (though I've never tried).

Answer 2

> The two frameworks aren't binary compatible >

Actually the Desktop version can load and run CF assemblies.

Answer 3

1. Create a class library for the compact framework.
2. Add a reference to that library from your .exe project (Desktop or Mobile)
3. Profit!

Seriously, I don't know why the top answer is so top. You don't need two separate projects at all. Also i'm not in love with pre-processor directives, they're ugly and require additional knowledge about the project when playing with the build parameters. It is much more pretty to outsource all the incompatible bits and pieces to an interface (IPlaformServices or such like) or you could even just ask:

   if(Environment.OSVersion.Platform == PlatformID.WinCE)
   {
       // winCE specific     
   }
   else
   {
       // desktop specific
   }

Both of these are better solutions than preprocessor directives IMO.