委托

代码示例

1delegate void MessagePrinter();

1// 声明一个委托类型的变量，并使其指向一个方法
2MessagePrinter printer = new MessagePrinter(PrintHelloWorld);
3
4// 不使用构造函数，可以直接用方法指针初始化
5MessagePrinter printer2 = PrintHelloWorld;
6
7// 添加另一个方法，使委托指向它
8printer += PrintGoodBye;
9printer2 += PrintGoodBye;
10
11// 调用委托
12printer();
13
14// 另一种调用委托的方式
15printer2.Invoke();
16
17// 返回 void 且不接受任何参数
18void PrintHelloWorld()
19{
20    Console.WriteLine("Hello World!");
21}
22
23// 返回 void 且不接受任何参数
24void PrintGoodBye()
25{
26    Console.WriteLine("Good bye!");
27}
28
29// 返回 void 且不接受任何参数
30delegate void MessagePrinter();

1namespace Delegates;
2
3public class Dog
4{
5    public string Name { get; set; }
6
7    public Dog(string name)
8    {
9        Name = name;
10    }
11
12    public void Bark()
13    {
14        Console.WriteLine($"{Name} says bark! bark!");
15    }
16}

1using Delegates;
2
3// 创建 Dog 类的实例
4Dog dog = new Dog("Roxie");
5Dog dog2 = new Dog("Buzz");
6
7// 绑定方法
8MessagePrinter printer = dog.Bark;
9printer += dog2.Bark;
10
11// 调用委托
12printer();
13
14delegate void MessagePrinter();

1// 创建同类型的委托
2MessagePrinter printer1 = SurroundWithHyphens;
3MessagePrinter printer2 = SurroundWithStars;
4MessagePrinter printer3 = SurroundWithStars;
5
6// 合并委托
7MessagePrinter printer4 = printer1 + printer2 + printer3;
8
9// 调用委托
10printer4("Hello World!");
11
12void SurroundWithStars(string message)
13{
14    Console.WriteLine($"***{message}***");
15}
16
17void SurroundWithHyphens(string message)
18{
19    Console.WriteLine($"---{message}---");
20}
21
22delegate void MessagePrinter(string message);

1MessagePrinter printer = SurroundWithHyphens;
2printer += SurroundWithStars;
3
4MethodInvoker(printer, "some message");
5
6void MethodInvoker(MessagePrinter printerDelegate, string message)
7{
8    // 使用空条件运算符防止委托为 null 时引发异常
9    printerDelegate?.Invoke(message);
10}
11
12void SurroundWithStars(string message)
13{
14    Console.WriteLine($"***{message}***");
15}
16
17void SurroundWithHyphens(string message)
18{
19    Console.WriteLine($"---{message}---");
20}
21
22delegate void MessagePrinter(string message);

1// 实例化泛型委托
2MathOperator<int, long> op1 = Adder;
3MathOperator<int, double> op2 = Divider;
4
5long sum = op1(5, 6);
6double divisionResult = op2(7, 2);
7
8Console.WriteLine(sum);
9Console.WriteLine(divisionResult);
10
11long Adder(int firstNumber, int secondNumber)
12{
13    return firstNumber + secondNumber;
14}
15
16double Divider(int firstNumber, int secondNumber)
17{
18    return (double)firstNumber / secondNumber;
19}
20
21// 泛型委托
22delegate T2 MathOperator<T1, T2>(T1 operand1, T1 operand2);