列表ForEach中断

问题描述

有没有办法打破foreach扩展方法？ break关键字不能将扩展方法识别为有效的作用域。

  //不能编译ForEach（i => {System.Windows.MessageBox.Show（i.ToString（））; if（i> 2）break;}） ; 
 
 
 
 
 
 $ b 
编辑：从问题中删除linq p> 
 
 
 
 
 
请注意代码只是一个示例，显示break在扩展方法中不起作用...我真正想要的是用户能够中止处理列表.. UI线程有一个中止变量和for循环只是当用户点击取消按钮时打破。现在，我有一个正常的循环，但我想看看是否有可能做的扩展方法。
解决方案
把这个称为 List< T>  Foreach与LINQ之间可能更准确。
 
 
 
尽管如此，没有办法打破这个循环。主要是因为它实际上并不是一个循环。这是一个方法，它需要在循环内部调用一个委托。 
 
 
 
创建一个具有中断能力的ForEach是非常直接的，但是
 
 pre $  public delegate void ForEachAction< T>（T value，ref bool doBreak）; 
 public static void ForEach< T>（this IEnumerable< T> enumerable，ForEachAction< T> action）{
 var doBreak = false; 
 foreach（var cur in enumerable）{
 action（cur，ref doBreak）; 
 if（doBreak）{
 break; 
 
 
 
 
 
你可以重写你的代码如下所示： 
 
 
  Enumerable.Range（0,10）
 .ForEach（（int i，ref bool doBreak） => {
 System.Windows.MessageBox.Show（i.ToString（））; 
 if（i> 2）{doBreak = true;} 
}）; 
  
 
is there a way to break out of the foreach extension method?  The "break" keyword doesn't recognize the extension method as a valid scope to break from.
//Doesn't compile
Enumerable.Range(0, 10).ToList().ForEach(i => { System.Windows.MessageBox.Show(i.ToString()); if (i > 2)break; });
Edit: removed "linq" from question
note the code is just an example to show break not working in the extension method... really what I want is for the user to be able to abort processing a list.. the UI thread has an abort variable and the for loop just breaks when the user hits a cancel button.  Right now, I have a normal for loop, but I wanted to see if it was possible to do with the extension method.
 解决方案 
It's probably more accurate to call this a List<T> Foreach vs. a LINQ one.
In either case though no there is no way to break out of this loop.  Primarily because it's not actually a loop per say.  It's a method which takes a delegate that is called inside a loop.   
Creating a ForEach with break capability is fairly straight forward though
public delegate void ForEachAction<T>(T value, ref bool doBreak);
public static void ForEach<T>(this IEnumerable<T> enumerable, ForEachAction<T> action) {
    var doBreak = false;
    foreach (var cur in enumerable) {
        action(cur, ref doBreak);
        if (doBreak) {
            break;
        }
    }
}
You could then rewrite your code as the following 
Enumerable.Range(0,10)
    .ForEach((int i,ref bool doBreak) => {
        System.Windows.MessageBox.Show(i.ToString()); 
        if ( i > 2) {doBreak = true;}
    });
                        
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