using System;
using System.Reflection;

namespace MyNamespace
{
    class MyClass
    {
        static void Main(string[] args)
        {
            // Load the external DLL
            Assembly assembly = Assembly.LoadFile("path/to/mydll.dll");

            // Get the type of the class you want to invoke
            Type type = assembly.GetType("MyNamespace.MyClass");

            // Create an instance of the class
            object instance = Activator.CreateInstance(type);

            // Invoke a method on the class
            MethodInfo method = type.GetMethod("MyMethod");
            method.Invoke(instance, null);
        }
    }
}