C#

using System;
using System.Reflection;

namespace RunArbitraryClasss
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class RunArbitraryClasss
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static int Main(string[] args)
		{
			// Get the program running.
			RunArbitraryClasss oRunArbitraryClasss = new RunArbitraryClasss();

			return(oRunArbitraryClasss.Run(args));
		}

		public int Run(string[] args)
		{
			// Get a list of valid types.
			Type [] aTypes = System.Reflection.Assembly.GetExecutingAssembly().GetTypes();

			foreach(Type oCurrType in aTypes)
			{
				if(oCurrType.ToString() == args[0] && oCurrType.IsSubclassOf(Type.GetType("RunArbitraryClasss.ValidRunnableClass")))
				{
					// Get the constructor for the class to invoke the run method on.
					ConstructorInfo ci = oCurrType.GetConstructor(Type.EmptyTypes);

					// Create an instance of the class that is derived from 
					// ValidRunnableClass. This will give us our prototype for invoking the 
					// Run method on the subclass.
					ValidRunnableClass vrc = (ValidRunnableClass) ci.Invoke(null);
					
					// Drop the first arg from the args list.
					string [] passArgs = new string [args.Length - 1];
					int i = 0;
					for(i = 1; i < args.Length; i++)
					{
						passArgs[i - 1] = args[i];
					}

					// Execute the target class.
					return(vrc.Run(passArgs));
				}
			}

			throw new Exception("A class was specified that is not subclassed from ValidRunnableClass!");
		}
	}

	abstract class ValidRunnableClass
	{
		abstract public int Run(string [] args);
	}

	class RunnableClass : ValidRunnableClass
	{
		public override int Run(string [] args)
		{
			Console.Write("I'm a runnable class:");
			
			foreach(string tempStr in args)
				Console.Write(" {0}", tempStr);

			return(0);
		}
	}

	class NonRunnableClass
	{
		public int Run(string [] args)
		{
			Console.Write("I'm a NON-runnable class:");
			
			foreach(string tempStr in args)
				Console.Write(" {0}", tempStr);

			return(0);
		}
	}
}