datagrid and data bound datatable

Here is the issue;

I have a datagrid that has a datatable bound to it. If the grid is unsorted I can detect all the rows that the user selects if the user multi selects rows. The issue comes when the datagrid gets sorted on a column. Then the datatable some how becomes "unbound" or unsorted and the two no longer line up correctly. ie, some one sorts on column 1 then selects rows 1, 2, and 3. These rows are not the same as the unsorted rows 1, 2, and 3. Since I need to know the sorted selected rows, this causes some issues for me.

Any help would be appreciated.

EDIT: This is all done in C#

 

that's correct. The indexing for the rows has been changed when you sort. what you probably want to do is maintain a list<T> of selected rows.