设计模式：职责链模式

职责链模式（Chain of Responsibility）：使多个对象都有机会处理请求，从而避免请求的发送者和接受者之间的耦合关系。将这个对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止。

namespace ChainDesign
{
    public abstract class Handler
    {
        protected Handler successor;
        public void SetSuccessor(Handler successor)
        {
            this.successor = successor;
        }
        public abstract void HandleRequest(int request);
    }
    public class ConcreteHandler1 : Handler
    {
        public override void HandleRequest(int request)
        {
            if(request>=0&&request<10)
            {
                Console.WriteLine("{0}处理请求{1}", this.GetType().Name, request);
            }
            else if(successor!=null)
            {
                successor.HandleRequest(request);
            }
        }
    }
    public class ConcreteHandler2 : Handler
    {
        public override void HandleRequest(int request)
        {
            if (request >= 10 && request < 20)
            {
                Console.WriteLine("{0}处理请求{1}", this.GetType().Name, request);
            }
            else if (successor != null)
            {
                successor.HandleRequest(request);
            }
        }
    }
    public class ConcreteHandler3 : Handler
    {
        public override void HandleRequest(int request)
        {
            if (request >= 20 && request < 30)
            {
                Console.WriteLine("{0}处理请求{1}", this.GetType().Name, request);
            }
            else if (successor != null)
            {
                successor.HandleRequest(request);
            }
        }
    }
}

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