To reproduce do the following:

1. Use Virtual Scrolling

2. Add following behavior for making datagrod selection as Rows

<ig:Selection CellClickAction="Row" CellSelectType="None" RowSelectType="Multiple" >                         </ig:Selection>

3. Scroll through the data little.

4. Select a row in WebDataGrid.

5. Have a button or any other way make a Ajax postback.

When we do this: On the server side when we try to get the selected rows; using :

WebDataGrid1.Behaviors.Selection.SelectedRows it gives us right number of rows selected by user;

But when you rows are all null.

e.g. WebDataGrid1.Behaviors.Selection.SelectedRow[0] will be null.