[2008] Validating integer and decimal fields in datagridview cell

I'm wondering what is the best practice for validating a number field in a datagridview cell. I'm using the CellValidating event and testing for the columns that are number fields. I'll just show my code.

Code:

Private Sub grdPOLineItems_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles grdPOLineItems.CellValidating Try If Me.grdPOLineItems.Rows.Count < 1 Then Exit Sub 'is the user clicking on the column headers? If e.RowIndex = -1 Then Exit Sub 'is it the new row? If Me.grdPOLineItems.Rows(e.RowIndex).IsNewRow Then Exit Sub If e.FormattedValue = Nothing Then Exit Sub 'here is where we divide the waters between decimal price fields and integer quantity fields If e.ColumnIndex = Me.grdPOLineItems.Columns("clmUnitPrice").DisplayIndex Then Dim newValue As Decimal If Decimal.TryParse(e.FormattedValue, newValue) Then 'are there no changes being made? If newValue = CDec(Me.grdPOLineItems.Rows(e.RowIndex).Cells(e.ColumnIndex).Value) Then Exit Sub Else 'if the value can't be parsed into a decimal, then it is invalid e.Cancel = True End If ElseIf Me.integerColumns.Contains(e.ColumnIndex) Then 'deals with integer columns Dim newValue As Integer If Integer.TryParse(e.FormattedValue, newValue) Then If newValue = CInt(Me.grdPOLineItems.Rows(e.RowIndex).Cells(e.ColumnIndex).Value) Then Exit Sub Else e.Cancel = True End If End If Catch ex As Exception MessageBox.Show(ex.Message, AppName) End Try End Sub

The lines in green are simple tests I use to determine if there is any point in continuing with the procedure.

The "clmUnitPrice" is a decimal field column. The integerColumns collection is merely a list of integer values, initialized earlier on, that holds the display indices of a list of columns that only allow integer values.

The problem I am having is with the line in red. Say, for instance, a user enters a cell that is tied to an Int32 or Decimal typed column. In this cell the user types a value, then decides, no, this is the wrong column, so the user backspaces to String.Empty and tries to tab to the next column. I'm getting a massive cell error stating that "" cannot be converted to type Int32. What boggles me is, if the user enters that cell, and then decides to tab out with only string.empty as the value, the system accepts it just fine. But if they type and then backspace to string.empty, then it snags.

I replaced the red code with the following:

If e.formattedvalue = nothing then
e.cancel = true
exit sub
end if

This code makes the system really snag. Then it won't even let me exit my application by clicking the "X" in the control box. I have to close it through Visual Studio.

Anyway, my question is, first, maybe, is there anything obviously wrong with my code? Or second, is there a more standard and better way to validate Cell Values in VB?

Thanks,
Jerome