Linq to select all pairs from a list

I'm looking for a C# LINQ statement that will return all pairs from a list.

I've seen solution of the form:

var combinations = from item1 in list
                   from item2 in list
                   where item1 < item2
                   select Tuple.Create(item1, item2);

My problem is the (item1 < item2). What if these are objects that can't be compared?

The non-Linq solution would be something like:

for (int I=0; I < list.Count; ++I)
    for (int j = I+1; j < list.Count; ++j)
        pairs.Add(new Pair(list[I], list[j]);

So if list = {a,b,c,d,e}
the pairs would be:
{a,b}
{a,c}
{a,d}
{a,e}
{b,c}
{b,d}
{b,e}
{c,d}
{c,e}
{d,e}

(An item is not paired with itself)
And we don't want both {a,e} and {e,a}. Just the first one.