To call a class method, you need to first create it. To create an instance of your class, you need to make the following sequence of calls. First you need to create a wrapper object class in the domain that you downloaded dll
ObjectHandle objWrap = news.CreateInstance(tt.FullName, "MyType");
This function returns an ObjectHandle object that is used to transfer an object (in a minimized state) between several application domains.
Your cjb class must necessarily inherit from the MarshalByRefObject class , which allows access to an object across application domain boundaries.
After that, you can call the Unwrap function to get an instance of a class created in another domain.
// Unwrapps the proxy to the MyType object created in the other AppDomain. MyType testObj = (MyType)objWrap.Unwrap();
After that, you can call the function of this class.