Here is the code:

using System;

namespace ProxyExample
{
	class Class1
	{
		[STAThread]
		static void Main(string[] args)
		{
			Console.WriteLine("--- ProxyExample started ---\n");

			Proxy proxy = new Proxy(new BusinessObject());
			BusinessObject bizObject = (BusinessObject)proxy.GetTransparentProxy();

			bizObject.A = 17;
			bizObject.B = 23;
			bizObject.Multiply();

			Console.WriteLine("Press any key to quit");
			Console.ReadLine();
		}
	}
}

using System;

namespace ProxyExample
{
	public class BusinessObject : MarshalByRefObject
	{
		private int a = 0;
		private int b = 0;

		public BusinessObject()
		{
		}

		public int Multiply()
		{
			return a * b;
		}

		public int A
		{
			get { return this.a; }
			set { this.a = value; }
		}

		public int B
		{
			get { return this.b; }
			set { this.b = value; }
		}
	}
}

using System;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Proxies;

namespace ProxyExample
{
	public class Proxy : RealProxy
	{
		private object target;

		public Proxy(MarshalByRefObject target) : base(target.GetType())
		{
			this.target = target;
		}

		public override IMessage Invoke(IMessage msg)
		{
			IMethodCallMessage call = msg as IMethodCallMessage;

			preprocess();

			Console.WriteLine("method called: " + call.MethodName);
			IMessage returnMsg = RemotingServices.ExecuteMessage(
				(MarshalByRefObject)this.target, call);

			postprocess();

			return returnMsg;
		}

		private void preprocess()
		{
			Console.WriteLine("before method call...");
		}

		private void postprocess()
		{
			Console.WriteLine("after method call...\n");
		}

		public object Target
		{
			get { return this.target; }
			set { this.target = value; }
		}

	}
}