Question

I’d like to use the LINQ TakeWhile function on LINQ to Objects. However, I also need to know the first element that “broke” the function, i.e. the first element where the condition was not true.

Is there a single function to get all of the objects that don’t match, plus the first that does?

For example, given the set {1, 2, 3, 4, 5, 6, 7, 8},

mySet.MagicTakeWhile(x => x != 5);

=> {1, 2, 3, 4, 5}

Answer 1

I think you can use SkipWhile, and then take the first element.

var elementThatBrokeIt = data.SkipWhile(x => x.SomeThing).Take(1);

UPDATE

If you want a single extension method, you can use the following:

public static IEnumerable<T> MagicTakeWhile<T>(this IEnumerable<T> data, Func<T, bool> predicate) {
    foreach (var item in data) {
        yield return item;
        if (!predicate(item))
            break;
    }
}