多平台统一管理软件接口,如何实现多平台统一管理软件接口
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2024-02-03
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(/*arguments*/)); // 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 IDrawingObjects 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 IShapes 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 IDrawingObjects event before the object is drawn. PreDrawEvent?.Invoke(this, EventArgs.Empty); Console.WriteLine("Drawing a shape."); // Raise IShapes 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(); } } } /* Output: Sub1 receives the IDrawingObject event. Drawing a shape. Sub2 receives the IShape event. */范围和索引为访问序列中的单个元素或范围提供了简洁的语法。在本教程中,你将了解:对某个序列中的范围使用该语法。了解每个序列开头和末尾的设计决策。了解 Index 和 Range 类型的应用场景。 ...
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