What's your favorite LINQ to Objects operator which is not built-in? [closed]

Answer 1

One, Two, MoreThanOne, AtLeast, AnyAtAll

public static bool One(this IEnumerable enumerable)
{
    using (var enumerator = enumerable.GetEnumerator())
        return enumerator.MoveNext() && !enumerator.MoveNext();
}

public static bool Two(this IEnumerable enumerable)
{
    using (var enumerator = enumerable.GetEnumerator())
        return enumerator.MoveNext() && enumerator.MoveNext() && !enumerator.MoveNext();
}

public static bool MoreThanOne(this IEnumerable enumerable)
{
    return enumerable.Skip(1).Any();
}

public static bool AtLeast(this IEnumerable enumerable, int count)
{
    using (var enumerator = enumerable.GetEnumerator())
        for (var i = 0; i < count; i++)
            if (!enumerator.MoveNext())
                return false;
    return true;
}

public static bool AnyAtAll(this IEnumerable enumerable)
{
    return enumerable != null && enumerable.Any();
}