List contains in List check

.net, c#, linq

Solution

The one liner approach of Rawling and Tim is very nice, but it has one little gotcha: `b` is iterated twice. If that is a problem for you, you could use an iterator based approach. This can be created as an extension method:

public static bool IsContainedWithinInOrder<T>(this IEnumerable<T> values,
                                               IEnumerable<T> reference)
{
    using(var iterator = reference.GetEnumerator())
    {
        foreach(var item in values)
        {
            do
            {
                if(!iterator.MoveNext())
                    return false;
            } while(!Equals(iterator.Current, item));
        }

        return true;
    }
}

This would iterate both sequences only once and overall is more lightweight. You would call it like this:

b.IsContainedWithinInOrder(a);

Please forgive the name of the method...

Problem

Original source