I'm not sure why would have an issue unless maybe you have a different version of Dev Ex installed. maybe if you remove and re-add the dev ex references it will work.

Anyways what I did was create a class that inherits from dataset so I can then drag and drop business objects onto it and it adds them to the dataset so you end up with a typed datset with relations etc. So far it works well for me I am not doing any zillion recrods grids or reports so there could be some issues.

Now I have a typed data set in my toolbar that contains whatever business objects I dropped onto it. I can then drag and drop it onto a form or report and use it as a data source.

If I drop it on a form with a Dev Ex grd I can assign it as the data source

and datamember

The end result is a grid with master child navigation

or a report with child bands