How to prevent others from using my .Net assembly?

Question

I have an assembly which should not be used by any application other than the designated executable. Please give me some instructions to do so.

Answer 1

You can sign the assembly and the executable with the same key and then put a check in the constructor of the classes you want to protect:

public class NotForAnyoneElse {
  public NotForAnyoneElse() {
    if (typeof(NotForAnyoneElse).Assembly.GetName().GetPublicKeyToken() != Assembly.GetEntryAssembly().GetName().GetPublicKeyToken()) {
      throw new SomeException(...);
    }
  }
}

Answer 2

In .Net 2.0 or better, make everything internal, and then use Friend Assemblies

http://msdn.microsoft.com/en-us/library/0tke9fxk.aspx

This will not stop reflection. I want to incorporate some of the information from below. If you absolutely need to stop anyone from calling, probably the best solution is:

1. ILMerge the .exe and .dll
2. obfuscate the final .exe

You could also check up the call stack and get the assembly for each caller and make sure that they are all signed with the same key as the assembly.