Proper implementation for RemoveAll<T>

gistfile1.cs

public static void RemoveAll<T>(this List<T> list, Func<T, bool> filter)
{
    if (filter == null)
        throw new ArgumentException("filter");

    if (list == null)
        throw new ArgumentException("list");

    int index = 0;
    while ((index < list.Count) && !filter(list[index]))
    {
        index++;
    }

    if (index >= list.Count)
    {
        return;
    }
    
    int secondaryCounter = index + 1;
    while (secondaryCounter < list.Count)
    {
        while ((secondaryCounter < list.Count) && filter(list[secondaryCounter]))
        {
            secondaryCounter++;
        }
        if (secondaryCounter < list.Count)
        {
            list[index++] = list[secondaryCounter++];
        }
    }

    list.RemoveRange(index, list.Count - index);
}