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

Answer 1

CountUpTo

static int CountUpTo(this IEnumerable source, int maxCount)
{
    if (maxCount == 0)
        return 0;

    var genericCollection = source as ICollection; 
    if (genericCollection != null) 
        return Math.Min(maxCount, genericCollection.Count);

    var collection = source as ICollection; 
    if (collection != null)
        return Math.Min(maxCount, collection.Count);

    int count = 0;
    foreach (T item in source)
        if (++count >= maxCount)
            break;
    return count;
}