Question

I want to pass only e.Trip of my string.Format to the method referenced in tripChoose. As of now, it tried to pass a string not formatted for the method. If I could just pass the Trip part of the string, it would work. Any suggestions?

private void LoadExpenseListSums()
{
    expenseTotalSelect.Items.Clear();
    var sortedList=
        from e in roster
        group e by e.Trip into expenseCollect
        select new { Trip = expenseCollect.Key, SumAmount = expenseCollect.Sum(e => e.Amount) };
    foreach (var e in sortedList)
        tripChoose.Items.Add(string.Format("{0} | ${1}", e.Trip, e.SumAmount));
}

Answer 1

Right, now we actually know what we’re dealing with, I suspect you want something like this:

private void LoadExpenseListSums()
{
    expenseTotalSelect.Items.Clear();
    var dateSorted =
        from e in roster
        group e by e.Trip into tripGroup
        select new { Trip = tripGroup.Key,
                     Text = string.Format("{0} | ${1}",
                                          tripGroup.Key,
                                          tripGroup.Sum(e => e.Amount) };
    tripChoose.DataSource = dateSorted;
    tripChoose.DisplayMember = "Text";
    tripChoose.ValueMember = "Trip";
}

This makes a few assumptions:
ase,
– roster is an in-memory collection: if it’s not, you’ll probably need an AsEnumerable call before the formatting, to make that happen locally
– Anonymous types work with data binding; I’m not sure whether that’s the case, but I’d hope it is

You then use the SelectedValue member later on to find the trip ID.