Remove duplicates from a List in C#

Question

Anyone have a quick method for de-duplicating a generic List in C#?

Answer 1

Sort it, then check two and two next to each others, as the duplicates will clump together.

Something like this:

list.Sort();
Int32 index = list.Count - 1;
while (index > 0)
{
    if (list[index] == list[index - 1])
    {
        if (index < list.Count - 1)
            (list[index], list[list.Count - 1]) = (list[list.Count - 1], list[index]);
        list.RemoveAt(list.Count - 1);
        index--;
    }
    else
        index--;
}

Notes:

• Comparison is done from back to front, to avoid having to resort list after each removal
• This example now uses C# Value Tuples to do the swapping, substitute with appropriate code if you can't use that
• The end-result is no longer sorted