推荐的方法来检查序列是否为空 [英] Recommended way to check if a sequence is empty

问题描述

一个方法返回一个序列IEnumerable<T>，现在您要检查它是否为空.您如何建议这样做?我正在寻找良好的可读性和良好的性能.

A method returns a sequence, IEnumerable<T>, and you now want to check if it is empty. How do you recommend doing that? I'm looking for both good readability and good performance.

第一种也是最明显的方法是检查计数是否大于零:

The first and most obvious way is to check that the count is greater than zero:

if(sequence.Count() == 0)

具有不错的可读性，但是性能很差，因为它实际上必须遍历整个序列.

Has decent readability, but terrible performance since it has to actually go through the whole sequence.

我有时使用的一种方法如下:

A method that I sometimes use is the following:

if(!sequence.Any())

(据我所知)这不必遍历整个序列，但是可读性有点落后和尴尬. (如果我们要检查序列是否为 not 为空，则阅读效果会更好).

This doesn't (as far as I know) have to go through the whole sequence, but the readability is a bit backwards and awkward. (Reads a lot better if we are checking that the sequence is not empty though).

另一种选择是在尝试捕获中使用First，如下所示:

Another option is to use First in a try-catch, like this:

try
{
    sequence.First();
}
catch(InvalidOperationException)
{
    // Do something
}

这不是一个非常漂亮的解决方案，并且可能也更慢，因为它使用了异常和填充.当然可以通过使用FirstOrDefault来防止这种情况，除非序列中的第一项实际上是默认值；)

Not a very pretty solution, and probably slower too, since it is using exceptions and stuff. Could prevent that by using FirstOrDefault of course, except you would have a big problem if the first item in the sequence actually was the default value ;)

那么，还有其他方法可以检查序列是否为空吗?您通常使用哪一个?您建议使用哪一个?

So, any other ways to check if a sequence is empty? Which one do you usually use? Which one do you recommend to use?

注意:为了获得最佳的可读性，我可能会将上述片段之一放在IsEmpty扩展方法中，但我仍然很好奇，因为我必须在该方法中做点事情以及:p

Note: For optimal readability I would probably put one of the above snippets in an IsEmpty extension method, but I am still curious since I would have to do something inside that method as well :p

推荐答案

我个人会使用!sequence.Any().

如果确实需要，则可以始终编写自己的扩展方法:

If you really need to, you could always write your own extension method:

public static bool IsEmpty<T>(this IEnumerable<T> source)
{
    return !source.Any();
}

然后您可以编写:

if (sequence.IsEmpty())

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