Question

I’m in the situation that I have to use an unsigned third party .NET DLL in my signed application. So I decided to load that library dynamically at run-time:

var asm = Assembly.LoadFrom("THIRDPARTYASSEMBLY.DLL");

There is a static class in the DLL which I defined an interface for in my application and used GetUninitializedObject() to load the class:

var obj = FormatterServices.GetUninitializedObject(asm.GetType("NAMESPACE.CLASS")) as IMyInterface;

Although the class I’m trying to load is not abstract (It’s a public static class) I get this error at runtime:

System.MemberAccessException was unhandled: Cannot create an
abstract class.

Obviously I can’t use CreateInstance method because the static class doesn’t have any constructors.

So what would you suggest? I want to:

• Invoke a public static method from that library. (I’m currently using InvokeMember().)
• Get a Custom Type property.
• Handle a few Custom Events in my application.

Thanks in advance.

Answer 1

Instead of trying to call the method dynamically, you could try to strong name the third party dll.

You will need a key to strong name the dll with. You could either use the one you are already using for your own dll, or create a new one for this purpose (using sn -k).

To strong name the already compiled assembly:

1. Open a visual studio command prompt (to get the tools into your path).
2. Generate il from the assembly:
   ildasm ThirdParty.dll /out:ThirdParty.il
3. Rename the original ThirdParty.dll to something else.
4. Generate a new dll, strong naming it as you do so:
   ilasm ThirdParty.il /dll /key=MyKey.snk

This will result in a new ThirdParty.dll which will be strong named with the key you have specified. You can then add a direct reference to it and call the methods directly as you normally would.