命令模式

计算器例子：

  public class Command : ICommand
    {
        private Queue<decimal> queue = new Queue<decimal>();
        public decimal[] GetResults=>queue.ToArray();
        private Receiver _receiver;
        public Receiver Receiver { get => _receiver; set => _receiver=value; }

        public decimal Execute(params decimal[] items)
        {
            var result = _receiver.Cal(items);
            queue.Enqueue(result);
            return result;
        }

        public decimal Reset()
        {
            return queue.Dequeue();
        }
    }

    public class Add : Receiver { public decimal Cal(params decimal[] items) { return items.Aggregate((x, y) => x + y); } }
    public class Sub : Receiver { public decimal Cal(params decimal[] items) { return items.Aggregate((x, y) => x - y); } }
    public class Mul : Receiver { public decimal Cal(params decimal[] items) { return items.Aggregate((x, y) => x * y); } }
    public class Div : Receiver { public decimal Cal(params decimal[] items) { return items.Aggregate((x, y) => x/ y); } }
    public interface Receiver
    {
        decimal Cal(params decimal[] items);
    }
    
    public interface ICommand
    {
        decimal Execute(params decimal[] items); 
        Receiver Receiver { get; set; }
    }
    public interface IClient
    {
        decimal Execute(params decimal[] items);
        decimal Reset();
    }
    
    public class Client:IClient
    {
        private Queue<decimal> queue = new Queue<decimal>();
        private ICommand _command;
        public Client(ICommand command)
        {
            _command = command;
        }

        public decimal Execute(params decimal[] items)
        {
            decimal result = _command.Execute(items);
            queue.Enqueue(result);
            return result;
        }

        public decimal Reset()
        {
           return queue.Dequeue();
        }
    }

客户端实现：

Command addCommand = new Command();
addCommand.Receiver = new Add();
IClient client = new Client(addCommand);
var result = client.Execute(1, 2, 3, 4, 5);
result = client.Reset();

Command subCommand = new Command();
subCommand.Receiver = new Sub();