.NET事件 - 从预订一个事件阻止用户 [英] .NET events - blocking subscribers from subscribing on an event

问题描述

让我们说我有一个处理器接口暴露的事件 - OnProcess。通常情况下，实现者做处理。因此，我可以放心地订阅此事件上，并确保它会被解雇。但一个处理器并不做处理 - 因此，我想阻止用户向所有本就可以了。我能做到这一点？在代码换句话说下面我想最后一行抛出一个异常：

  VAR emptyProcessor =新EmptyProcessor（）; 
 emptyProcessor.OnProcess + = event_handler; //此行应该抛出一个异常。 
  

解决方案

 类EmptyProcessor ：IProcessor {
 
 [过时（EmptyProcessor.OnProcess不应该直接访问，真）] 
公共事件的EventHandler OnProcess {
加{抛出新NotImplementedException（:( ）;} 
拆下{} 
} 
} 
  

在这种情况下，对过时的真正参数导致编译时异常这样：

  EmptyProcessor处理器1 =新EmptyProcessor（）; 
 IProcessor分享帮助=新EmptyProcessor（）; 
 
 processor1.OnProcess + =处理; //<  - 编译时错误
 processor2.OnProcess + =处理; //<  - 运行时错误
  

Let's say I have a "Processor" interface exposing an event - OnProcess. Usually the implementors do the processing. Thus I can safely subscribe on this event and be sure it will be fired. But one processor doesn't do processing - thus I want to prevent subscribers to subscibe on it. Can I do that? In other words in the code below I want the last line to throw an exception:

var emptyProcessor = new EmptyProcessor();
emptyProcessor.OnProcess += event_handler; // This line should throw an exception.

解决方案

class EmptyProcessor : IProcessor {

    [Obsolete("EmptyProcessor.OnProcess should not be directly accessed", true)]
    public event EventHandler OnProcess { 
        add { throw new NotImplementedException(" :( "); }
        remove { }
    }
}

In this situation, the true parameter on Obsolete causes a compile-time exception. so:

EmptyProcessor processor1 = new EmptyProcessor();
IProcessor processor2 = new EmptyProcessor();

processor1.OnProcess += handler;  // <-- compile-time error
processor2.OnProcess += handler;  // <-- run-time error

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