using System;

using ServiceBus;

​

public class Program

{

    public static void Main()

    {

        var messageType = "ServiceBus.MessageA";

        var type = Type.GetType(messageType);       

        ILastExecutedMessage result = (ILastExecutedMessage)Activator.CreateInstance(type);

        result.LastExecuted = DateTime.UtcNow;

        //Send

    }   

}

​

namespace ServiceBus 

{

    public class MessageA : ILastExecutedMessage

    {

        public DateTime LastExecuted {get;set;}

    }

    public class MessageB : ILastExecutedMessage

    {

        public DateTime LastExecuted {get;set;}

    }

    public interface ILastExecutedMessage

    {

        DateTime LastExecuted {get;set;}

    }

}