Question

Like,

List<string> a = {"a0","a1","a2","a3"};

Using LINQ, how do I take a[2] and remove it?

Answer 1

Sounds as if you are looking for the List.RemoveAt method instead:

a.RemoveAt(2);

Edit:

how can i find out it is the before the last index

So you want to remove the second last instead of the one with index 2, you can use the Count property to find it. There’s absolutely no need to use Linq here:

if(a.Count > 1)
    a.RemoveAt(a.Count - 2);

Demo