Private Sub dgv_DataError(sender As Object, _
        e As System.Windows.Forms.DataGridViewDataErrorEventArgs) _
        Handles dgv.DataError
 
    If e.ColumnIndex < 0 Then
       e.Cancel = True : Exit Sub
    End If
 End Sub

public int Compare(object x, object y)
    {
        if (x == null || x == DBNull.Value)
           {
               if (y == null || y == DBNull.Value) return 0;
               return 1;
           }
        if (y == null || y == DBNull.Value) return -1;
 
        return ((F)x).CompareTo((T)y);
    }