I want to allow the user delete all rows, but the last one.

Tring your method your method I finally obtained a stange unhandleld exception, without any stacktrace:

Internal error: can't convert to DestinationValue.

Infragistics v6

I tried one more time... it worked that time )

I'm not entirely sure what you mean. 

If you don't want to allow the user to delete rows, why are you cancelling the event ?
Instead, set the property AllowDelete to false:
UltraGrid1.DisplayLayout.Override.AllowDelete = Infragistics.Win.DefaultableBoolean.False

Anyway, if you still want to keep the event, you could try this: 

        RemoveHandler UltraGrid1.BeforeRowsDeleted, AddressOf UltraGrid1_BeforeRowsDeleted
        UltraGrid1.Rows.Last().Delete()
        AddHandler UltraGrid1.BeforeRowsDeleted, AddressOf UltraGrid1_BeforeRowsDeleted

Make sure you have any rows to delete first, or you could get an exception.

Thank you, it worked... partially....

Previously I denied the last row deletion (by user only)

  Private Sub grdFilter_BeforeRowsDeleted(ByVal sender As Object, ByVal e As Infragistics.Win.UltraWinGrid.BeforeRowsDeletedEventArgs) Handles grdFilter.BeforeRowsDeleted
    If grdFilter.RowCount = e.Rows.Count Then e.Cancel = True
  End Sub

So that did from the above delete code a infinite loop...

Now, I would like to be able to remove that last row by code, but do not allow user to remove it...

Hey,

This seems to work for me:

        While UltraGrid1.Rows.Count > 0
            UltraGrid1.Rows(0).Delete(False)
        End While

Kind regards,

Michael

I am afraid I have no DataSource on the grid, because I fill-in manually.