gistfile1.cs

public interface ICommandMessageHandler<TCommand>
{
	void Execute(TCommand message);
}

public interface ICommandMessageHandler : ICommandMessageHandler<object>
{
}

public abstract class Command<T> : ICommandMessageHandler
{
	public void Execute(object message)
	{
		Execute((T) message);
	}

	protected abstract void Execute(T message);
}

public interface IAmSynchronized : ICommandMessageHandler
{
}

public class SynchronizedCommandDecorator : ICommandMessageHandler
{
	readonly IAmSynchronized _handler;
	readonly ISynchronizer _synchronizer;

	public SynchronizedCommandDecorator(IAmSynchronized handler, ISynchronizer synchronizer)
	{
		_handler = handler;
		_synchronizer = synchronizer;
	}

	public void Execute(object message)
	{
		// call _handler
	}
}

public class ConfigureEnvironmentCommand : Command<ConfigureEnvironmentMessage>
{
	protected override void Execute(ConfigureEnvironmentMessage message)
	{
	}
}

public class ConfigureEnvironmentMessage
{
}

public class ConfigureEnvironmentCommandSync : Command<ConfigureEnvironmentMessage>, IAmSynchronized
{
	protected override void Execute(ConfigureEnvironmentMessage message)
	{
	}
}