It sounds like you might want something like:
for (int i = 0; i < list.Count - 1; i++)
{
for (int j = i + 1; j < list.Count; j++)
{
// Use list[i] and list[j]
}
}
You definitely can do this with LINQ:
var pairs = from i in Enumerable.Range(0, list.Count - 1)
from j in Enumerable.Range(i + 1, list.Count - i - 1)
select Tuple.Create(list[i], list[j]);
I'm not sure it's any clearer though...
EDIT: Another alternative which is less efficient, but potentially clearer:
var pairs = from i in Enumerable.Range(0, list.Count - 1)
let x = list[i]
from y in list.Skip(i + 1)
select Tuple.Create(x, y);
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