GridFilterBar in a GridDataBoundGrid

What I'm trying to do is to have the grid display empty and then allow the user to utilize the filter bar to determine what to display. The GridFilterBar will only show the values from the displayed grid column in the combobox dropdown list. How can I manually load the filter's dropdown list with all possible distinct values from the datasource?

Here is one thing that would be simple to try to see if this will give you the behavior you are looking for. Go ahead and fill your datatable and set it as the datasource in the grid. Then directly apply a RowFilter on its default view that returns no rows. This means the grid should appear empty, but the underlying full datatable is there as its datasource. Then create your GridFilterBar. Its should create the dropdowns based on the contents of the full table. Attached is a sample.