我有2 的IEnumerable＆LT; INT＆GT;

IEnumerable<int> x;
IEnumerable<int> y;

这是确定是否y中任何int是present在x问题最好最佳方式 目前我使用：

What is the best best way to determine if any int in y is present in the x? Currently I'm using:

return x.Intersect<int>(y).Count() > 0;

通过更快的循环难道是显著和测试每个单独的？

Would it be significantly faster to loop through and test each individually?

foreach (int i in x)
{
    foreach (int j in y)
    {
        if (i == j) return true;
    }
}
return false;

的列表是相对较轻，具有和不超过50个整数英寸×4 y中，如果，在考虑事项。

The lists are relatively light, with not more than 50 ints in x and 4 in y if that matters in the consideration.

推荐答案

这将是最快使用的 任何方法代替的 计数方法：

It would be fastest to use the Any method instead of the Count method:

return x.Intersect<int>(y).Any();

这假定 的IEnumerable＆LT; INT＆GT; 实现不也实现ICollection<int>.在这种情况下，计数（的情况下，其中的IEnumerable＆LT; T＆GT; 工具的ICollection＆LT; T＆GT ; ）是一个O（N）操作，而任何是总是的一个O（1）操作。 （因为只检查了的单的元素）。然而，的行为计数是一个实现细节，你不应该依赖于这一点。

This assumes that the IEnumerable<int> implementation doesn't also implement ICollection<int>. In that case, Count (in the case where IEnumerable<T> implements ICollection<T>) is an O(N) operation while Any is always an O(1) operation. (as it only checks for a single element). However, the behavior of Count is an implementation detail, and you shouldn't rely on that.

我已经写了这个更深入在博客中这将详细介绍何时使用计数（）与任何（）。总结：

I've written about this more in-depth in a blog post that goes into detail about when to use Count() vs. Any(). In summary:

DO 使用 Enumerable.Any 扩展方法来检查序列中的元素的存在。 不要在比较中使用 Enumerable.Count 扩展方法与零，如以下在语义上是等价的： sequence.Count（）== 0 ！sequence.Any（） DO use Enumerable.Any extension method to check for the existence of elements in the sequence. DO NOT use Enumerable.Count extension method in comparisons against zero, as the following are semantically equivalent: sequence.Count() == 0 !sequence.Any() sequence.Count！= 0 sequence.Any（） sequence.Count != 0 sequence.Any()