Datagridcombobox value not displaying

Question

I have a DataGridView (called DataGridViewSecurity) in VB.net (Visual Studio 2010) which is bound to a DataTable (called DataTableSecurity) in a DataSet (called DataSetSecurity). I have added a nonbound column (called nSecurityComboBox) that I set based on an integer field (called nSecLevel) in the DataTable. After setting the combobox, it doesn't display anything in the combobox, but when you select the combobox, the 5 values in it's items collection show.

Here's the code I'm using to add a record to the DataTable and then to set the combobox:

Sub Foo()
.
.
.
    DataSetSecurity.Tables(0).Rows.Add(New Object() {sName, sID, sSec})
    ComboCell_Select(nRow, 3, DataGridViewSecurity, sSecRecs.nSecLevel)
    MessageBox.Show("Value for the combo set at " + DataGridViewSecurity.Rows(nRow).Cells(3).Value.ToString)
.
.
.
End Sub

Private Sub ComboCell_Select(ByVal dgvRow As Integer, _
                             ByVal dgvCol As Integer, _
                             ByRef DGV As DataGridView,
                             ByRef nComboBoxRow As Int16)

    Try
        Dim CBox As DataGridViewComboBoxCell = CType(DGV.Rows(dgvRow).Cells(dgvCol), DataGridViewComboBoxCell)
        Dim CCol As DataGridViewComboBoxColumn = CType(DGV.Columns(dgvCol), DataGridViewComboBoxColumn)

        CBox.Value = CCol.Items(nComboBoxRow)
        DGV.UpdateCellValue(dgvCol, dgvRow)

        'MessageBox.Show("New value in the combo box = " + CBox.Value.ToString)
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
End Sub

The messagebox.show in Foo shows the correct value for the combobox, but nothing is displayed. Anyone see what I'm doing wrong?

Thanks.

-NCGrimbo

Answer 1

In the end, I found some C# code that I converted to VB.net to fix the issue. Here's the code:

Private Sub DataGridViewSecurity_EditingControlShowing(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) Handles DataGridViewSecurity.EditingControlShowing
    Dim cellComboBox As ComboBox = TryCast(e.Control, ComboBox)
    If cellComboBox IsNot Nothing Then
        ' make sure the handler doen't get registered twice
        RemoveHandler cellComboBox.SelectionChangeCommitted, AddressOf Me.CellComboBoxOnSelectionChangeCommitted
        AddHandler cellComboBox.SelectionChangeCommitted, AddressOf Me.CellComboBoxOnSelectionChangeCommitted
    End If
End Sub

Private Sub CellComboBoxOnSelectionChangeCommitted(ByVal sender As Object, ByVal e As EventArgs)
    Dim comboBox As DataGridViewComboBoxEditingControl = TryCast(sender, DataGridViewComboBoxEditingControl)
    If sender Is Nothing Then
        Return
    End If
    If comboBox.SelectedItem Is Nothing Then
        Return
    End If
    If Me.DataGridViewSecurity.CurrentCell.Value = comboBox.SelectedItem Then
        Return
    End If

    Me.DataGridViewSecurity.CurrentCell.Value = comboBox.SelectedItem

End Sub

Answer 2

If I understand the question right, all values are in the combobox just not being selected by default properly? I think I just had this problem a few days ago, here's what I have now.

'Create the combobox column
Dim comboBox As New DataGridViewComboBoxColumn()

'Add some stuff to the combobox
comboBox.Items.Add("FirstItem")
comboBox.Items.Add("SecondItem")

'Select the first item
comboBox.DefaultCellStyle.NullValue = comboBox.Items(0) 

'Now add the whole combobox to the DataGridView
dgvItems.Columns.Add(comboBox)

Hope this helps!