Linq Contains()是否检查HashSet? [英] Does Linq Contains() check for HashSet?

问题描述

有时HashSet通过属性作为IEnumerable公开.

Sometimes a HashSet is exposed through a property as an IEnumerable.

众所周知，对于enumerable.Count()，代码将检查它是否是一个集合，因此它不会枚举整个列表，而是采用了快捷方式.

It is well known that for enumerable.Count() the code checks if it is a collection, so it doesn't enumerate the whole list, but takes a shortcut.

是否有使用Linq版本的enumerable.Contains(x)和HashSets的类似检查?

Is there any similar check for using the Linq version of enumerable.Contains(x) and HashSets?

推荐答案

来自参考源，是的，虽然不是直接的:

From the reference source, yes it does, though not directly:

public static bool Contains<TSource>(this IEnumerable<TSource> source, TSource value) {
    ICollection<TSource> collection = source as ICollection<TSource>;
    if (collection != null) return collection.Contains(value);
    return Contains<TSource>(source, value, null);
}

如果源枚举实现了 ICollection<T> (和 HashSet<T> 确实)，然后它使用集合的 Contains 方法.

If the source enumerable implements ICollection<T> (and HashSet<T> does), then it uses the collection's Contains method.

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