接口可以声明事件。 下面的示例演示如何在类中实现接口事件。 这些规则基本上都与实现任何接口方法或属性时的相同。

在类中实现接口事件

在类中声明事件，然后在相应区域中调用它。

namespace ImplementInterfaceEvents { public interface IDrawingObject { event EventHandler ShapeChanged; } public class MyEventArgs : EventArgs { // class members } public class Shape : IDrawingObject { public event EventHandler ShapeChanged; void ChangeShape() { // Do something here before the event… OnShapeChanged(new MyEventArgs()); // or do something here after the event. } protected virtual void OnShapeChanged(MyEventArgs e) { ShapeChanged?.Invoke(this, e); } } }

示例

下面的示例演示如何处理不太常见的情况：类继承自两个或多个接口，且每个接口都具有相同名称的事件。 在这种情况下，你必须为至少其中一个事件提供显式接口实现。 为事件编写显式接口实现时，还必须编写 add 和 remove 事件访问器。 通常这些访问器由编译器提供，但在这种情况下编译器不提供它们。

通过提供自己的访问器，可以指定两个事件是由类中的同一个事件表示，还是由不同事件表示。 例如，如果根据接口规范应在不同时间引发事件，可以在类中将每个事件与单独实现关联。 在下面的示例中，订阅服务器确定它们通过将形状引用转换为 IShape 或 IDrawingObject 接收哪个 OnDraw 事件。

namespace WrapTwoInterfaceEvents{ using System; public interface IDrawingObject { // Raise this event before drawing // the object. event EventHandler OnDraw; } public interface IShape { // Raise this event after drawing // the shape. event EventHandler OnDraw; } // Base class event publisher inherits two // interfaces, each with an OnDraw event public class Shape : IDrawingObject, IShape { // Create an event for each interface event event EventHandler PreDrawEvent; event EventHandler PostDrawEvent; object objectLock = new Object(); // Explicit interface implementation required. // Associate IDrawingObject's event with // PreDrawEvent #region IDrawingObjectOnDraw event EventHandler IDrawingObject.OnDraw { add { lock (objectLock) { PreDrawEvent += value; } } remove { lock (objectLock) { PreDrawEvent -= value; } } } #endregion // Explicit interface implementation required. // Associate IShape's event with // PostDrawEvent event EventHandler IShape.OnDraw { add { lock (objectLock) { PostDrawEvent += value; } } remove { lock (objectLock) { PostDrawEvent -= value; } } } // For the sake of simplicity this one method // implements both interfaces. public void Draw() { // Raise IDrawingObject's event before the object is drawn. PreDrawEvent?.Invoke(this, EventArgs.Empty); Console.WriteLine("Drawing a shape."); // Raise IShape's event after the object is drawn. PostDrawEvent?.Invoke(this, EventArgs.Empty); } } public class Subscriber1 { // References the shape object as an IDrawingObject public Subscriber1(Shape shape) { IDrawingObject d = (IDrawingObject)shape; d.OnDraw += d_OnDraw; } void d_OnDraw(object sender, EventArgs e) { Console.WriteLine("Sub1 receives the IDrawingObject event."); } } // References the shape object as an IShape public class Subscriber2 { public Subscriber2(Shape shape) { IShape d = (IShape)shape; d.OnDraw += d_OnDraw; } void d_OnDraw(object sender, EventArgs e) { Console.WriteLine("Sub2 receives the IShape event."); } } public class Program { static void Main(string[] args) { Shape shape = new Shape(); Subscriber1 sub = new Subscriber1(shape); Subscriber2 sub2 = new Subscriber2(shape); shape.Draw(); // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); } }}

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