Being in the office this week, under Jeff's firm nagging about recording more videos, I can continue the tutorials about using DXGrid for WPF.
Here's one about how to create an unbound column for the datagrid.
I note on watching it that I neglected to show that the unbound column is fully supported by the grid's sorting and grouping facilities with no extra code. You just click on the column header to sort on the unbound data, or drag the column header to the group box to group on it. Didn't even think about this at the time, sigh.