C# 多播委托 注意事项

委托的基本概念就不说了，我先简单说一下什么是多播委托。

包含多个方法的委托就是多播委托。

简单地举了例子:

delegate void MyDelegate();

        static void Main(string[] args)
        {

            MyDelegate my1 = Write;

            my1 += Read;

            Console.ReadLine();
        }

        static void Write() 
        {
            Console.WriteLine("Write this is using named method");
        }

        static void Read()
        {
            Console.WriteLine("Read this is using named method");
        }

 

多播委托识别"+","+=","-","-=" 运算符，以从委托中删除或添加方法调用。

 

多播委托实际上就是多个委托的集合，如果在实行多播委托时，其中一个方法抛出异常，那么整个迭代都会停止。

　　　　　　　delegate void MyDelegate();

        static void Main(string[] args)
        {
            try
            {
                MyDelegate my1 = Write;
                my1 += Read;
                my1();
            }
            catch(Exception) 
            {
                Console.WriteLine("Error caught");
            }

            Console.ReadLine();
        }

        static void Write() 
        {
            Console.WriteLine("Write this is using named method");
            throw new Exception("Err in Write");
        }

        static void Read()
        {
            Console.WriteLine("Read this is using named method");
            throw new Exception("Err in Read");
        }

得到的结果是：

Write this is using named method

Error caught

为了避免这种方法，需要自己迭代列表。下面是修改后的代码

        delegate void MyDelegate();

        static void Main(string[] args)
        {
           
            MyDelegate my1 = Write;
            my1 += Read;

            Delegate[] dls = my1.GetInvocationList();

            foreach (MyDelegate dl in dls)
            {
                try
                {
                    dl();
                }
                catch(Exception)
                {
                    Console.WriteLine("Error caught");
                }
            }

            Console.ReadLine();
        }

        static void Write() 
        {
            Console.WriteLine("Write this is using named method");
            throw new Exception("Err in Write");
        }

        static void Read()
        {
            Console.WriteLine("Read this is using named method");
            throw new Exception("Err in Read");
        }

得到的结果是：

Write this is using named method

Error caught

Read this is using named method

Error caught