1.委托聲明

2.委托入門實例

namespace ConsoleApplication1
{
    
    public delegate void methodDelegate(string str);
    class Program
    {
        static void Main(string[] args)
        {
            Student student = new Student();
            Teacher teacher = new Teacher("王老師");
            methodDelegate methodDelegate1 = new methodDelegate(student.getStudentName);
            methodDelegate1 += teacher.getTeacherName; //可以指向不同類中的方法！
            //methodDelegate1 += teacher.getClassName; 指向簽名不符的方法時提示錯誤！
            methodDelegate1.Invoke("張三");
            Console.ReadLine();
        }
    }

    class Student
    {
        private String name = "";
        public Student (String _name)
        {
            this.name = _name ;
        }
        public Student() {}
        public void getStudentName(String _name) 
        {
            if (this.name != "" )
                Console.WriteLine("Student's name is {0}", this.name);
            else
                Console.WriteLine("Student's name is {0}", _name);
        }
    }

    class Teacher
    {
        private String name;
        public Teacher(String _name)
        {
            this.name = _name;
        }
        public void getTeacherName(String _name)
        {
            if (this.name != "")
                Console.WriteLine("Teacher's name is {0}", this.name);
            else
                Console.WriteLine("Teacher's name is {0}", _name);
        }
        public string getClassName() 
        {
            return "Eanlish";
        }
    }
}

上面代碼中實現對委托的調用

最後將被調用的委托輸出

3.委托的實現方式

  第一種：常規實現

private delegate String getAString( string parament);
        static void Main(String []args)
        {
            int temp = 40;
            getAString stringMethod = new getAString(temp.ToString); //傳遞temp.ToString調用委托

            Console.WriteLine("String is {0}", stringMethod());  //stringMethod()調用已經接受參數的委托
            Console.ReadLine();
        }

 第二種：多播委托

 getAString stringMethod = new getAString(temp.ToString);
         stringMethod += temp.ToString;
         stringMethod -= temp.ToString;  

　　這種調用之後，按照接受參數的次數， 委托會生成一個列表，每用+=調用一次，會增加一個列表項，-=調用一次，會移除一個列表項。

 第三種：委托數組

    當我們定義委托 讓委托形成一個數組的時候，我們可以通過遍歷數組的方式來調用它

delegate double Operations(double x);

    class Program
    {
        static void Main()
        {
            Operations[] operations =
            {
               MathOperations.MultiplyByTwo,
               MathOperations.Square
            };

            for (int i = 0; i < operations.Length; i++)
            {
                Console.WriteLine("Using operations[{0}]:", i);
                DisplayNumber(operations[i], 2.0);
                DisplayNumber(operations[i], 7.94);
                Console.ReadLine();
            }
        }

        static void DisplayNumber(Operations action, double value)
        {
            double result = action(value);
            Console.WriteLine(
               "Input Value is {0}, result of operation is {1}", value, result);
        }
    }

    struct MathOperations
    {
        public static double MultiplyByTwo(double value)
        {
            return value * 2;
        }

        public static double Square(double value)
        {
            return value * value;
        }
    }

上面實例中

 將委托定義好

之後就可以遍歷它

委托的實現方式還有三種  持續更新中！