Question

I want to load a type at run time using reflection. Below are the steps:

1. Load the assembly using Assembly.LoadFile(assemblyPath);
2. Use the GetType method to obtain the type
3. Use Activator.CreateInstance to create the instance of type.

Below is my code:

Assembly assembly = Assembly.LoadFile(assemblyName);
Type type = assembly.GetType("RomanConerter.Converter");
object obj = Activator.CreateInstance(type);

Problem I am facing is with the last line. My Converter has one method name Add. But I cannot access this method using obj.

Note: The assembly which I am trying to load in in other project, and I have hasrd coded the path.

Can anyone help me out please ?

Answer 1

This all depends on whether the type RomanConverter.Converter is available to you in your calling application (i.e. that contains the code you’ve posted). If so, then you just cast.

If not – then you can late-bind the method with reflection (as others have said) or use dynamic, but imho you’d do better to use a common base or interface:

/* common interface used in both your code and the external DLL */
public interface ICanAdd {
  object Add(object source);
}

(I’m guessing the signature here)

And then change this plug-in type of yours to:

namespace RomanConverter {
  public class Converter : ICanAdd {
    object Add(object source){
      //TODO: implement
    }
  }
}

Now when you get the object from Activator.CreateInstance you just cast to ICanAdd:

ICanAdd obj = (ICanAdd)Activator.CreateInstance(type);

Now you can call the method.