这是使用C＃创建和使用事件的示例
using System;namespace Event_Example{ //First we have to define a delegate that acts as a signature for the //function that is ultimately called when the event is triggered. //You will notice that the second parameter is of MyEventArgs type. //This object will contain information about the triggered event. public delegate void MyEventHandler(object source, MyEventArgs e); //This is a class which describes the event to the class that recieves it. //An EventArgs class must always derive from System.EventArgs. public class MyEventArgs : EventArgs { private string EventInfo; public MyEventArgs(string Text) { EventInfo = Text; } public string GetInfo() { return EventInfo; } } //This next class is the one which contains an event and triggers it //once an action is performed. For example, lets trigger this event //once a variable is incremented over a particular value. Notice the //event uses the MyEventHandler delegate to create a signature //for the called function. public class MyClass { public event MyEventHandler OnMaximum; private int i; private int Maximum = 10; public int MyValue { get { return i; } set { if(value <= Maximum) { i = value; } else { //To make sure we only trigger the event if a handler is present //we check the event to make sure it's not null. if(onMaximum != null) { onMaximum(this, new MyEventArgs("You've entered " + value.ToString() + ", but the maximum is " + Maximum.ToString())); } } } } } class Program { //This is the actual method that will be assigned to the event handler //within the above class. This is where we perform an action once the //event has been triggered. static void MaximumReached(object source, MyEventArgs e) { Console.WriteLine(e.GetInfo()); } static void Main(string[] args) { //Now lets test the event contained in the above class. MyClass MyObject = new MyClass(); MyObject.onMaximum += new MyEventHandler(MaximumReached); for(int x = 0; x <= 15; x++) { MyObject.MyValue = x; } Console.ReadLine(); } }}
