Remove list elements at given indices

Question

I have a list which contains some items of type string.

List lstOriginal;

I have another list which contains idices which sh

Answer 1

My in-place deleting of given indices as handy extension method. It copies all items only once so it is much more performant if large amount of indicies is to be removed.

It also throws ArgumentOutOfRangeException in case where index to remove is out of bounds.

 public static class ListExtensions 
 {
    public static void RemoveAllIndices(this List list, IEnumerable indices)
    {
        //do not remove Distinct() call here, it's important
        var indicesOrdered = indices.Distinct().ToArray();
        if(indicesOrdered.Length == 0)
            return;

        Array.Sort(indicesOrdered);

        if (indicesOrdered[0] < 0 || indicesOrdered[indicesOrdered.Length - 1] >= list.Count)
            throw new ArgumentOutOfRangeException();

        int indexToRemove = 0;
        int newIdx = 0;

        for (int originalIdx = 0; originalIdx < list.Count; originalIdx++)
        {
            if(indexToRemove < indicesOrdered.Length && indicesOrdered[indexToRemove] == originalIdx)
            {
                indexToRemove++;
            }
            else
            {
                list[newIdx++] = list[originalIdx];
            }
        }

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