C# 为什么对AddEventHandler的调用不起作用?
我有以下概念验证课程:C# 为什么对AddEventHandler的调用不起作用?,c#,.net,events,reflection,delegates,C#,.net,Events,Reflection,Delegates,我有以下概念验证课程: private class SourceMock { public event PropertyChangedEventHandler TestEvent; public void Raise() { if (this.TestEvent != null) { this.TestEvent(this, new PropertyC
private class SourceMock
{
public event PropertyChangedEventHandler TestEvent;
public void Raise()
{
if (this.TestEvent != null)
{
this.TestEvent(this, new PropertyChangedEventArgs("S"));
}
}
}
private class HandlerMock
{
public HandlerMock()
{
}
public void PropertyHandler(object sender, PropertyChangedEventArgs e)
{
}
}
那么,如果我执行以下操作,它就会起作用:
SourceMock sourceMock = new SourceMock();
HandlerMock handler = new HandlerMock();
sourceMock.GetType().GetEvent("TestEvent").AddEventHandler(sourceMock, new PropertyChangedEventHandler(handler1.PropertyHandler));
但如果执行以下操作,则不起作用:
SourceMock sourceMock = new SourceMock();
HandlerMock handler = new HandlerMock();
sourceMock.GetType().GetEvent("TestEvent").AddEventHandler(sourceMock, new EventHandler<PropertyChangedEventArgs>(handler1.PropertyHandler));
SourceMock SourceMock=newsourcemock();
HandlerMock handler=new HandlerMock();
sourceMock.GetType().GetEvent(“TestEvent”).AddEventHandler(sourceMock,新的EventHandler(handler1.PropertyHandler));
因为我得到以下异常:
System.ArgumentException:类型为的对象
'System.EventHandler'1[System.ComponentModel.PropertyChangedEventArgs]'
无法转换为类型
“System.ComponentModel.PropertyChangedEventHandler”
我希望有一个处理事件的泛型类,但我不能将委托用作泛型类型,我必须使用EventArgs,这给了我第二种语法(非工作语法)
关于如何克服这个问题有什么想法吗
编辑:这就是我想要实现的目标
我需要一个类来截获事件,并在引发事件之前进行处理(比如计数、过滤、重新排序等等)。客户端不会注册到事件,但会要求此类将其注册到事件。我认为签名如下:
public class EventHandlerService<T> where T : EventArgs
{
public void Register(object eventSource, string eventName, EventHandler<T> handler)
}
公共类EventHandlerService,其中T:EventArgs
{
公共无效寄存器(对象eventSource、字符串eventName、EventHandler)
}
当事件发生时,服务将根据内部算法调用所有已注册的处理程序
在内部,它与EventInfo类一起工作,而与非从EventHandler派生的EventHandler不一起工作,因此这个问题。事件的委托类型不必继承自
EventHandler
/EventHandler
。因此,这里的泛型可能是多余的:
public class EventHandlerService
{
/// <example>
/// Use this overload, when delegate type for the event isn't inherited from EventHandler/EventHandler{T}.
/// <code>
/// service.Register(someObj, "SomeEvent", new PropertyChangedHandler(TheHandler));
/// </code>
/// </example>
public void Register(object eventSource, string eventName, Delegate handler)
{
// do the work here
}
/// <example>
/// Use this overload, when delegate type for the event is inherited from EventHandler{T}.
/// <code>
/// service.Register<FooEventArgs>(someObj, "SomeEvent", TheHandler);
/// </code>
/// </example>
public void Register<T>(object eventSource, string eventName, EventHandler<T> handler)
where T : EventArgs
{
Register(eventSource, eventName, handler);
}
/// <example>
/// Use this overload, when delegate type for the event is inherited from EventHandler.
/// <code>
/// service.Register(someObj, "SomeEvent", TheHandler);
/// </code>
/// </example>
public void Register(object eventSource, string eventName, EventHandler handler)
{
// we need cast here to help compiler to find desired overload
Register(eventSource, eventName, (Delegate)handler);
}
}
问题中的特定问题可以通过以下方式解决:
var eventInfo = sourceMock.GetType().GetEvent("TestEvent");
eventInfo.AddEventHandler(sourceMock, Delegate.CreateDelegate(eventInfo.EventHandlerType, handler, "PropertyHandler"));
但是看起来您不需要解决它—只需删除泛型。您只是使用了错误的委托类型。EventHandler是一个完全不相关的类型。PropertyChangedEventHandler可以追溯到.NET1.x,该版本中还没有泛型。两个不同的委托类型永远不会被认为是相同的,即使它们的签名匹配。那么,有没有办法创建一个泛型类,在其他处理程序中接收PropertyChangedEventHandler处理程序并使用它们?使用EventHandler并将T指定为EventArgs可以解决问题,但对于从EventHandler继承的事件,则不行……感谢您指出这一点。我添加了X部分。