发送我自己的参数到事件处理程序？ [英] Sending My Own Arguments To A Event Handler?

问题描述

我正在与AssemblyResolve合作。这是我的代码，然后我的问题如下：

  var a = AppDomain.CurrentDomain; 
 a.AssemblyResolve + = new ResolveEventHandler（HandleIt）; 
 
私有程序集HandleIt（对象发件人，ResolveEventArgs参数）{
 //返回一个程序集
} 
  

所以我把HandleIt添加到我的AssemblyResolve事件中。如何将它添加到该事件并传递一个参数，如：

  a.AssemblyResolve + = new ResolveEventHandler（HandleIt AnArgument））; 
  

由于HandleIt接受参数，所以抛出我，但是当添加到AssemblyResolve事件。我会期望的东西如下：

  a.AssemblyResolve + = new ResolveEventHandler（HandleIt（aSender，someArgs））; 
  

所以是的，我只想在将其添加到HandleIt函数后发送另一个参数我的AssemblyResolve事件。

希望这是有道理的，谢谢。

附录：

  if（aBool）{
 a.AssemblyResolve + = new ResolveEventHandler（HandleA）; 
} 
 else {
 a.AssemblyResolve + = new ResolveEventHandler（HandleB）; 
} 
 
 HandleA（object sender，ResolveEventArgs args）{
句柄（true）; 
} 
 HandleB（object sender，ResolveEventArgs args）{
句柄（false）; 
} 
手柄（bool isA）{
 
} 
  

-vs -

  if（aBool）{
 a.AssemblyResolve + =（object s，ResolveEventArgs a ）=>处理（S，A，TRUE）; 
} 
 else {
 a.AssemblyResolve + =（object s，ResolveEventArgs a）=>处理（S，A，假）; 
} 
 
处理（对象发件人，ResolveEventArgs args，bool isA）{
 
} 
  

解决方案

当事件被触发时，如果要绑定其他参数，将传递参数传递给该方法，您可以使用lambdaexpression

  var a = AppDomain.CurrentDomain; 
 a.AssemblyResolve + =（object s，ResolveEventArgs a）=> HandleIt（S，A，someArgument）; 
 
私有程序集HandleIt（object sender，ResolveEventArgs args，SomeType arg）{
 //返回一个程序集
} 
  

其中someArgument是您要绑定的值。

这本质上是使用lambdas来做部分应用功能。 C＃不支持的东西，但在其他语言中很常见。当然，部分应用与F＃和Haskell等语言中存在的Currying非常密切相关（因为这个概念得到了Haskell Curry的名字）和各种其他的功能性语言。它们与结果类型不同。

它们都与闭包相关（因为上述代码中的概念被调用）和不支持部分应用的语言currying你可以使用闭包来完成类似的事情。但是请注意，关闭与部分应用程序的区别在于可能会产生一些令人惊讶的错误。例如。

  int i = 1; 
 Func< int> f =（）=>一世; 
 i = 2; 
 
 System.Console.WriteLine（f（））; 
  

打印 2 到控制台。因为closures将引用捕获到变量的值，而不是所述变量的值。这是for循环中常见的错误，当关闭for循环的循环变量时。

I'm working with AssemblyResolve specifically. Here is my code first, then my question follows:

var a = AppDomain.CurrentDomain;
a.AssemblyResolve += new ResolveEventHandler(HandleIt);

Private Assembly HandleIt(object sender, ResolveEventArgs args){
    //Does stuff, returns an assembly
}

So I add HandleIt to my AssemblyResolve event. How can I add it to that event and pass an argument with it like:

a.AssemblyResolve += new ResolveEventHandler(HandleIt(AnArgument));

This is throwing me off since HandleIt takes arguments, but none are explicetly passed when it is added to the AssemblyResolve event. I would expect something like:

a.AssemblyResolve += new ResolveEventHandler(HandleIt(aSender,someArgs));

So yeah, I just want to be able to send another argument to my HandleIt function when adding it to my AssemblyResolve event.

Hope that makes sense, thanks.

Addendum:

if(aBool){
    a.AssemblyResolve += new ResolveEventHandler(HandleA);
}
else{
    a.AssemblyResolve += new ResolveEventHandler(HandleB);
}

HandleA(object sender, ResolveEventArgs args){
    Handle(true);
}
HandleB(object sender, ResolveEventArgs args){
    Handle(false);
}
Handle(bool isA){

}

-vs-

if(aBool){
    a.AssemblyResolve += (object s, ResolveEventArgs a) => Handle(s,a,true);
}
else{
    a.AssemblyResolve += (object s, ResolveEventArgs a) => Handle(s,a,false);
}

Handle(object sender, ResolveEventArgs args, bool isA){

}

解决方案

When the event is fired arguments are passed to the method if you would like to bind additional arguments you could do that with a lambdaexpression

var a = AppDomain.CurrentDomain;
a.AssemblyResolve += (object s,ResolveEventArgs a) => HandleIt(s,a,someArgument);

Private Assembly HandleIt(object sender, ResolveEventArgs args, SomeType arg){
    //Does stuff, returns an assembly
}

where someArgument is the value you wish to bind.

This is essentially using lambdas to do a partial application of a function. Something that C# doesn't support directly but is very common in other languages. Partial application is very closely related to Currying that exists in languages such as F# and Haskell of course (since the concept gets it's name from Haskell Curry) and various other functional langauages. They differ in the result type.

They are both related to closures (as the concept in the above code is called) and in languages that don't support partial application or currying you can use closures to accomplish something similar. However be aware that closures differ from partial application in ways that can create some surprising bugs. E.g.

int i = 1;
Func<int> f = () => i;
i = 2;

System.Console.WriteLine(f());

prints 2 to the console. Because closures captures a reference to a variable not the value of said variable. This is a common error in for loops, when closing over the loop variable(s) of the for loop.

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