using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        AuditTrail.Context = new FooAuditTrailWriter();     

        AuditTrail.Write("someData", new byte[10]);

    }

}

​

public static class AuditTrail

{

    private static IAuditTrailWriter _context;

    public static IAuditTrailWriter Context

    {

        get 

        {

            if (_context == null)

            {

                _context = new MessageQueueAuditTrailWriter();

            }

            return _context;

        }

        set 

        {

            _context = value;

        }           

    }

    public static void Write(string dest, byte[] data)

    {

        Context.Write(dest, data);

    }       

}   

​

public interface IAuditTrailWriter

{

    void Write(string url, byte[] data);

}

public class MessageQueueAuditTrailWriter : IAuditTrailWriter

{   

    public void Write(string dest, byte[] data)

    {       

        // Write to message queue here

    }

}

public class FooAuditTrailWriter : IAuditTrailWriter

{

    public void Write(string dest, byte[] data)

    {

        // Write to Foo here

    }

}

​