问题描述
我在Windows Form C#程序的IF语句(在foreach循环中)中具有此Or条件:
I have this Or condition in an IF statement (in a foreach loop) in a Windows Form C# program:
if ((splittedFile.Count() != 3) || (splittedFile.Count() != 4))
continue;
，即使 splittedFile.Count()是3或4，它始终会继续执行 continue .问题是，如果我删除Or条件:
and it always does continue, even if splittedFile.Count() is 3 or 4.The thing is that if I remove the Or condition:
if ((splittedFile.Count() != 4))
continue;
它正常工作！！有什么想法吗?
it works properly!! Any ideas why?
推荐答案
这是正确的行为，您需要使用&& .
This is the correct behavior, you need to use &&.
原因是计数是固定数，例如 n .现在条件显示为:
The reason is that the count is fixed number, let's say n. Now the condition reads:
给出 n 为4，这意味着它不是3，因此测试成功，反之亦然.
Given n is 4, this means it is not 3, thus the test succeeds and vice versa.
编译器无法检测到这是真的，因为在两个 if 语句之间， Count()可能会更改(例如，在 multithreading中设置第二个线程在集合中添加内容或从集合中删除内容的位置.我同意，但是某些分析工具可以在某些情况下检测这种琐碎的行为.但总的来说，由于 Rice定理，无法进行这种分析.
A compiler can't detect this is trivially true, because between the two if statements, the Count() might change (for instance in a multithreading setting where the second thread would add/remove something to/from the collection). I agree however some analysis tools could be capable in some conditions to detect such trivial behavior. In general however such analysis can't be implemented because of Rice's theorem.
如果您使用&& ，则表达式为:
If you use &&, the expression reads:
因此这两个条件都应为真.换句话说，仅当 n 小于3且大于4时，条件成立.
Thus both conditions should be true. In other words only if n is less than three and greater than 4, the condition holds.
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