https://docs.microsoft.com/zh-cn/dotnet/standard/events/how-to-raise-and-consume-events 第一个示例演示如何引发和使用一个没有数据的事件。 它包含一个名为 using System; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Counter c = new Counter(new Random().Next(10)); c.ThresholdReached += c_ThresholdReached; Console.WriteLine("press 'a' key to increase total"); while (Console.ReadKey(true).KeyChar == 'a') { Console.WriteLine("adding one"); c.Add(1); } } static void c_ThresholdReached(object sender, EventArgs e) { Console.WriteLine("The threshold was reached."); Environment.Exit(0); } } class Counter { private int threshold; private int total; public Counter(int passedThreshold) { threshold = passedThreshold; } public void Add(int x) { total += x; if (total >= threshold) { OnThresholdReached(EventArgs.Empty); } } protected virtual void OnThresholdReached(EventArgs e) { EventHandler handler = ThresholdReached; if (handler != null) { handler(this, e); } } public event EventHandler ThresholdReached; } } 下一个示例演示如何引发和使用提供数据的事件。 EventHandler<TEventArgs> 委托与此事件关联,示例还提供了一个自定义事件数据对象的实例。 using System; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Counter c = new Counter(new Random().Next(10)); c.ThresholdReached += c_ThresholdReached; Console.WriteLine("press 'a' key to increase total"); while (Console.ReadKey(true).KeyChar == 'a') { Console.WriteLine("adding one"); c.Add(1); } } static void c_ThresholdReached(object sender, ThresholdReachedEventArgs e) { Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold, e.TimeReached); Environment.Exit(0); } } class Counter { private int threshold; private int total; public Counter(int passedThreshold) { threshold = passedThreshold; } public void Add(int x) { total += x; if (total >= threshold) { ThresholdReachedEventArgs args = new ThresholdReachedEventArgs(); args.Threshold = threshold; args.TimeReached = DateTime.Now; OnThresholdReached(args); } } protected virtual void OnThresholdReached(ThresholdReachedEventArgs e) { EventHandler<ThresholdReachedEventArgs> handler = ThresholdReached; if (handler != null) { handler(this, e); } } public event EventHandler<ThresholdReachedEventArgs> ThresholdReached; } public class ThresholdReachedEventArgs : EventArgs { public int Threshold { get; set; } public DateTime TimeReached { get; set; } } } 下一个示例演示如何声明事件的委托。 该委托名为 using System; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Counter c = new Counter(new Random().Next(10)); c.ThresholdReached += c_ThresholdReached; Console.WriteLine("press 'a' key to increase total"); while (Console.ReadKey(true).KeyChar == 'a') { Console.WriteLine("adding one"); c.Add(1); } } static void c_ThresholdReached(Object sender, ThresholdReachedEventArgs e) { Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold, e.TimeReached); Environment.Exit(0); } } class Counter { private int threshold; private int total; public Counter(int passedThreshold) { threshold = passedThreshold; } public void Add(int x) { total += x; if (total >= threshold) { ThresholdReachedEventArgs args = new ThresholdReachedEventArgs(); args.Threshold = threshold; args.TimeReached = DateTime.Now; OnThresholdReached(args); } } protected virtual void OnThresholdReached(ThresholdReachedEventArgs e) { ThresholdReachedEventHandler handler = ThresholdReached; if (handler != null) { handler(this, e); } } public event ThresholdReachedEventHandler ThresholdReached; } public class ThresholdReachedEventArgs : EventArgs { public int Threshold { get; set; } public DateTime TimeReached { get; set; } } public delegate void ThresholdReachedEventHandler(Object sender, ThresholdReachedEventArgs e); }
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