C#委托的协变性和逆变性
2021-06-11 18:05
标签：返回 委托 button memory new int and console 值类型 只要函数参数与委托兼容，就能创建委托实例。 只要返回值类型与委托兼容，就能创建委托实例 C#委托的协变性和逆变性 标签：返回 委托 button memory new int and console 值类型 原文地址：https://www.cnblogs.com/love-me-love-my-code/p/10556095.html逆变性
1 Button button = new Button();
2 //public delegate void EventHandler(object sender, EventArgs e);
3 button.Click += LogPlainEvent;
4 //public delegate void KeyPressEventHandler(object sender, KeyPressEventArgs e);
5 button.KeyPress += LogPlainEvent;
6 //public delegate void MouseEventHandler(object sender, MouseEventArgs e);
7 button.MouseClick += LogPlainEvent;
8
9 public void LogPlainEvent(object sender, EventArgs e)
10 {
11 }
协变性
1 public delegate Stream StreamFactory();
2
3 public MemoryStream GenerateData()
4 {
5 return new MemoryStream();
6 }
7
8 StreamFactory factory = GenerateData;
9 using (Stream stream = factory())
10 {
11 int data;
12 while((data = stream.ReadByte()) != -1)
13 {
14 Console.WriteLine(data);
15 }
16 }