Minimal command query separation

cqs.cs

namespace MakeMyDay 
{
        public interface ICommand { }

        public interface ICommandHandler<T> where T : ICommand
        {
                void Handle(T cmd);
        }

        public interface ICommandValidator<T> where T : ICommand
        {
		CommandValidationResult Validate(T basicsCommand);
	}

	public interface IQueryCommand : ICommand { }

	public interface IQueryResponse { }

	public interface ICommandDispatcher
	{
		void Dispatch<T>(T command)
			where T : ICommand;

		void DispatchAsync<T>(T command)
			where T : ICommand;

		CommandValidationResult Validate<T>(T command)
			where T : ICommand;

		CommandValidationResult ValidateAndDispatch<T>(T command)
			where T : ICommand;

		CommandValidationResult ValidateAndDispatchAsync<T>(T command)
			where T : ICommand;
		
		TR Query<TQ, TR>(TQ query)
			where TQ : IQueryCommand
			where TR : IQueryResponse;

		void QueryAsync<TQ, TR>(TQ query, Action<TR> callback)
			where TQ : IQueryCommand
			where TR : IQueryResponse;
	}

	public class CommandValidationResult
	{
		public bool Successful { get; private set; }
		public string ErrorCode { get; private set; }
		public Exception Exception { get; private set; }

		private CommandValidationResult(bool successful, string errorcode, Exception exception)
		{
			Successful = successful;
			ErrorCode = errorcode;
			Exception = exception;
		}

		public static CommandValidationResult Success() { return new CommandValidationResult(true, "", null); }
		public static CommandValidationResult Fail(string errorcode) { return new CommandValidationResult(false, errorcode, null); }
		public static CommandValidationResult Fail(string errorcode, Exception e) { return new CommandValidationResult(true, errorcode, e); }
		public static CommandValidationResult Fail(Exception e) { return new CommandValidationResult(true, "exception", e); }
	}

}