Any performance gain when using Any etc on List

Is there any performance gain when using Any开发者_开发问答 extension method than the old for loop way?

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In short, no; the performance is likely to be marginally poorer.

In practice, the brevity and clarity of this approach is going to have maintenance benefits over a loop and will be less prone to bugs.

Think of it this way: if you write 50 loops and forget to short-circuit evaluation in one of them, you'd have been better off using .Any in all 50.

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For indexed collections you could the following:

for(int i = 0; i < col.Length;i++)
{
  if (predicate(col[i]))
    return true;
}
return false;

but for non-indexed IEnumerable<T>, this is not possible, as it doesn't supply an indexer. This would be the implementation in the framework (via reflection):

public static bool Any<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
    if (source == null)
    {
        throw Error.ArgumentNull("source");
    }
    if (predicate == null)
    {
        throw Error.ArgumentNull("predicate");
    }
    foreach (TSource local in source)
    {
        if (predicate.Invoke(local))
        {
            return true;
        }
    }
    return false;
}

As it iterates over all elements of the IEnumerable<T>, there is no performance gain to be had. However, any "optimization" in this direction would fall under premature optimization, if there is a performance problem, it is more likely to be fixed in your algorithm than in this function.