delete row from datatable

[husky_doggy]

I can add rows and it automatically updates, work fine.
but when i try to delete a row, some can be delete some cant. but after all when I reload the list everything is unchanged..

 Dim response = MsgBox("Are you sure?", 4 Or 32, "")
            If response = MsgBoxResult.Yes Then
                rownum = SCD_allowedDataGrid.CurrentRowIndex
                SCD.SCD_allowed.Rows(rownum).Delete()
                Me.SCD_allowedDataGrid.Update()
              
            End If

then i try this: i got an error " Update requires a valid DeleteCommand when passed DataRow collection with deleted rows."
ok...i think i need a deletecommand.
DELETE FROM [SCD allowed]
WHERE ???? <<< what do i put here if i want to delete a selected row?

 Dim response = MsgBox("Are you sure?", 4 Or 32, "")
            If response = MsgBoxResult.Yes Then
                rownum = SCD_allowedDataGrid.CurrentRowIndex
                SCD.SCD_allowed.Rows(rownum).Delete()
               Me.SCD_allowedTableAdapter.Update(SCD.SCD_allowed)
              
            End If