Select all unique combinations of a single list, with no repeats, using LINQ

I have a list of numbers, and I need to create every possible unique combination of the numbers in the list, without repeats, using a LINQ query. So, for example, if I have { 1, 2, 3 }, the combinations would be 1-2, 1-3, and 2-3.

I currently use two for loops, like so:

for (int i = 0; i < slotIds.Count; i++)
{
    for (int j = i + 1; j < slotIds.Count; j++)
    {
        ExpressionInfo info1 = _expressions[i];
        ExpressionInfo info2 = _expressions[j];

        // etc...
    }
}

Is it possible to convert these two for loops to LINQ?

Thanks.