除去控制在一个循环 [英] Removing controls in a loop

问题描述

昨天我写了一段代码，以消除在满足一定标准形式的所有控件。天真地写吧，这就是我想出

Yesterday I wrote a piece of code to remove all the controls in a form that fulfills certain criteria. Writing it naively, this is what I come up with.

for (int i = 0; i < this.Controls.Count; ++i)
{
    if (this.Controls[i].Name.Length == 2)
    {
        this.Controls.Remove(this.Controls[i);
    }
}

但恰巧代码是错误的。然后，我将其更改为：

But it so happens that the code is wrong. I then change it to:

foreach (Control ctr in this.pbBoardImage.Controls)
{
    if (ctr.Length == 2)
    {
        this.Controls.Remove(ctr);
    }
}

但它仍然是不正确的。
我知道，正确的方法是：

But it still wasn't correct. I know that the correct way would be:

for (int i = this.Controls.Count - 1; i >= 0; i--)
{
    if (this.Controls[i].Name.Length == 2)
    {
        this.Controls.Remove(this.Controls[i]);
    }
}

但是它仍然没有感到优雅。我不能使用List.RemoveAll，因为this.Controls不是一个列表。所以，我能问一个更优雅的方式，最好不使用循环？

However it still doesn't feel elegant. I couldn't use List.RemoveAll, since this.Controls wasn't a List. So can I ask for a more elegant way, preferably without using a loop?

推荐答案

不知道为什么你不喜欢这答案......我突出的重要 RemoveAt移除;然而，在.NET 3.5的替代/ C＃3.0：LINQ：

Not sure why you didn't like this answer... I've highlighted the important RemoveAt; however, as an alternative in .NET 3.5/C# 3.0: LINQ:

        var qry = from Control control in Controls
                  where control.Name.Length == 2
                  select control;

        foreach(var control in qry.ToList()) {
            Controls.Remove(control);
        }

---

---

（原创）

您不能删除在的foreach - 它打破了迭代器。这里的一个普遍的方法是迭代的向后的：

You can't Remove within foreach - it breaks the iterator. A common approach here is to iterate backwards:

for (int i = this.Controls.Count - 1; i >= 0; i--) {
    if (this.Controls[i].Name.Length == 2) {
        this.Controls.RemoveAt(i); // <=========== *** RemoveAt
    }
}

这通过一次性问题等避免了。

This avoids the "off by one" issues, etc.

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