OK, I've figured out the original question... need to use .RowDropSettings(a => a.RowDropMapper()).
Second question - how do I do this with a treegrid? It doesn't have a RowDropSettings member.
Third question - with a treegrid, is it possible to only set AllowDropChild for certain nodes? For example - I want to use the TreeGrid as a master/detail grid, showing parent nodes on the first level and the detail records on the second. In this situation, it doesn't make sense to drop a detail record as a child of another detail record, or as a sibling of a master record, for that matter.
Thanks in advance...
Brian