Get previous/next item of a given item in a List<>

Question

Says I have this List : 1, 3, 5, 7, 9, 13

For example, given value is : 9, the previous item is 7 and the next item is 13

How can I achieve this using C#?

Answer 1

        List listInts = new List();
        listInts.AddRange(new int[] { 1, 3, 5, 7, 9, 13 });
        int index = listInts.IndexOf(3); //The index here would be "1"
        index++; //Check first if the index is in the length
        int element = listInts[index]; //element = 5