Compare two list elements with LINQ

Question

I'm trying to find a LINQ expression to compare two list elements.

What i want to do is:

List<int> _int = new List<int> { 1, 2, 3, 3, 4, 5};
_int.Where(x => x == _int[(_int.IndexOf(x)) + 1]);

Unfortunately, only the last +1 jumps out of the list's range.

How can I compare one item with its next in the list in a LINQ expression?

Answer 1

Not that nice but should work.

list.Where((index, item) => index < list.Count - 1 && list[index + 1] == item)

Or the following.

list.Take(list.Count - 1).Where((index, item) => list[index + 1] == item)

Answer 2

int i = 0;
_int.Where(x => 
{
    i++;
    return i < _int.Length && x == _int[i];
});

Answer 3

List<int> _int = new List<int> { 1, 2, 3, 3, 4, 5 };
Enumerable.Range(0, _int.Count - 1)
    .Select(i => new {val = _int[i], val2 = _int[i + 1]})
    .Where(check => check.val == check.val2)
    .Select(check => check.val);