datagrid combobox

[pmcguire]

I have derived a ComboBoxColumnS tyle that inherits DataGridColumnS tyle. It works fine except for one behavior. If the user selects a new value from the ComboBox's pulldown list on a brand new record, the ComboBoxColumn' s Commit event doesn't fire. If the user first edits a TextBox cell on the same New row, and THEN selects a new value for the ComboBox cell, Commit fires. What is going on and how do I get around it

Thanks

Pat

[Cor Ligthert]

Hi Pat,

I had this problems as well with I thought that was orignal the one you
mentioned, however it is already a year ago, (when you change the original
for firing alone it will shows the combobox to early in the header of the
datagrid).

I made some changes and it did work in my opinion as I wished, however I
never finished this project and therefore I am not complete sure if it
works.

Maybe you can try it?

Cor

Option Strict On
Option Explicit On
Public Class DataGridCombo
Inherits ComboBox
Public Sub New()
MyBase.New()
End Sub
End Class
Public Class DataGridComboCo lumnStyle
Inherits DataGridColumnS tyle
Private xMargin As Integer = 2
Private yMargin As Integer = 1
Private WithEvents Combo As DataGridCombo
Private mDisplayMember As String
Private mValueMember As String
Private mSource As CurrencyManager
Private mRowNum As Integer
Private OldVal As String = String.Empty
Private InEdit As Boolean = False
Public Sub New(ByRef DataSource As DataTable, ByVal DisplayMember As
Integer, ByVal ValueMember As Integer)
Combo = New DataGridCombo
mDisplayMember = DataSource.Colu mns.Item(Displa yMember).ToStri ng
mValueMember = DataSource.Colu mns.Item(ValueM ember).ToString
Combo.Visible = True
Combo.DataSourc e = DataSource
Combo.DisplayMe mber = mDisplayMember
Combo.ValueMemb er = mValueMember
Combo.DropDownS tyle = ComboBoxStyle.D ropDownList
Combo.Bounds = Rectangle.Empty
End Sub
Public Sub New(ByRef DataSource As DataTable, ByVal DisplayMember As
String, ByVal ValueMember As String)
Combo = New DataGridCombo
mDisplayMember = DisplayMember
mValueMember = ValueMember
Combo.Visible = True
Combo.DataSourc e = DataSource
Combo.DisplayMe mber = mDisplayMember
Combo.ValueMemb er = mValueMember
Combo.DropDownS tyle = ComboBoxStyle.D ropDownList
Combo.Bounds = Rectangle.Empty
End Sub
Protected Overloads Overrides Sub Abort(ByVal RowNum As Integer)
Debug.WriteLine ("Abort()")
RollBack()
HideComboBox()
EndEdit()
End Sub
Protected Overloads Overrides Function Commit(ByVal DataSource As
CurrencyManager , ByVal RowNum As Integer) As Boolean
HideComboBox()
If InEdit Then
Try
Dim Value As Object = Combo.SelectedV alue
If NullText.Equals (Value) Then
Value = DBNull.Value
End If
SetColumnValueA tRow(DataSource , RowNum, Value)
Catch
RollBack()
Return False
End Try
EndEdit()
End If
Return True
End Function
Protected Overloads Overrides Sub ConcedeFocus()
Combo.Visible = False
InEdit = False
End Sub
Protected Overloads Overrides Sub Edit(ByVal Source As CurrencyManager ,
_
ByVal Rownum As Integer, _
ByVal Bounds As Rectangle, _
ByVal [ReadOnly] As Boolean, _
ByVal InstantText As String, _
ByVal CellIsVisible As Boolean)
mSource = Source
mRowNum = Rownum
Combo.Text = ""
Dim OriginalBounds As Rectangle = Bounds
OldVal = Combo.Text
If CellIsVisible Then
Bounds.Offset(x Margin, yMargin)
Bounds.Width -= xMargin * 2
Bounds.Height -= yMargin
Combo.Bounds = Bounds
Combo.Visible = True
Else
Combo.Bounds = OriginalBounds
Combo.Visible = False
End If
Dim TextObject As Object = GetColumnValueA tRow(Source, Rownum)
If Not TextObject Is System.DBNull.V alue Then Combo.SelectedV alue =
TextObject.ToSt ring()
If Not InstantText Is Nothing Then
Combo.SelectedV alue = InstantText
End If
Combo.RightToLe ft = Me.DataGridTabl eStyle.DataGrid .RightToLeft
If InstantText Is Nothing Then
Combo.SelectAll ()
Else
Combo.Select(Co mbo.Text.Length , 0)
End If
If Combo.Visible Then
DataGridTableSt yle.DataGrid.In validate(Origin alBounds)
End If
InEdit = True
End Sub
Protected Overloads Overrides Function GetMinimumHeigh t() As Integer
Return Combo.Preferred Height + yMargin
End Function
Protected Overloads Overrides Function GetPreferredHei ght(ByVal g As
Graphics, ByVal Value As Object) As Integer
Debug.WriteLine ("GetPreferredH eight()")
Dim NewLineIndex As Integer = 0
Dim NewLines As Integer = 0
Do Until NewLineIndex = -1
NewLineIndex = DirectCast(Valu e, String).IndexOf ("r\n",
NewLineIndex + 1)
NewLines += 1
Loop
Return FontHeight * NewLines + yMargin
End Function
Protected Overloads Overrides Function GetPreferredSiz e(ByVal g As
Graphics, ByVal Value As Object) As Size
Dim Extents As Size = Size.Ceiling(g. MeasureString(G etText(Value), _
Me.DataGridTabl eStyle.DataGrid .Font))
Extents.Width += xMargin * 2 + DataGridTableGr idLineWidth
Extents.Height += yMargin
Return Extents
End Function

Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager , _
ByVal RowNum As Integer)
Paint(g, Bounds, Source, RowNum, False)
End Sub
Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
ByVal Bounds As Rectangle, _
ByVal Source As CurrencyManager , _
ByVal RowNum As Integer, _
ByVal AlignToRight As Boolean)
Dim objText As Object = GetColumnValueA tRow(Source, RowNum)
Dim Text As String = LookupDisplayVa lue(objText)
PaintText(g, Bounds, Text, AlignToRight)
End Sub
Protected Overloads Sub Paint(ByVal g As Graphics, ByVal Bounds As
Rectangle, ByVal Source As CurrencyManager , _
ByVal RowNum As Integer, ByVal BackBrush As Brush, ByVal ForeBrush As
Brush, ByVal AlignToRight As Boolean)
Dim objText As Object = GetColumnValueA tRow(Source, RowNum)
Dim Text As String = LookupDisplayVa lue(objText)
PaintText(g, Bounds, Text, AlignToRight)
End Sub
Protected Overloads Overrides Sub SetDataGridInCo lumn(ByVal Dg As
DataGrid)
MyBase.SetDataG ridInColumn(Dg)
If Not Combo.Parent Is Dg Then
If Not Combo.Parent Is Nothing Then
Combo.Parent.Co ntrols.Remove(C ombo)
End If
End If
If Not Dg Is Nothing Then Dg.Controls.Add (Combo)
End Sub
Protected Overloads Overrides Sub UpdateUI(ByVal Source As
CurrencyManager , ByVal RowNum As Integer, ByVal InstantText As String)
Combo.Text = GetText(GetColu mnValueAtRow(So urce, RowNum))
If Not (InstantText Is Nothing) Then
Combo.Text = InstantText
End If
End Sub
Private ReadOnly Property DataGridTableGr idLineWidth() As Integer
Get
If Me.DataGridTabl eStyle.GridLine Style = DataGridLineSty le.Solid
Then
Return 1
Else
Return 0
End If
End Get
End Property
Private Sub EndEdit()
InEdit = False
Invalidate()
End Sub
Private Function GetText(ByVal Value As Object) As String
If Value Is System.DBNull.V alue Then Return NullText
If Not Value Is Nothing Then
Return Value.ToString
Else
Return String.Empty
End If
End Function
Private Sub HideComboBox()
If Combo.Focused Then
Me.DataGridTabl eStyle.DataGrid .Focus()
End If
Combo.Visible = False
End Sub
Private Sub RollBack()
Combo.Text = OldVal
End Sub
Private Sub PaintText(ByVal g As Graphics, ByVal Bounds As Rectangle,
ByVal Text As String, ByVal AlignToRight As Boolean)
Dim BackBrush As Brush = New
SolidBrush(Me.D ataGridTableSty le.BackColor)
Dim ForeBrush As Brush = New
SolidBrush(Me.D ataGridTableSty le.ForeColor)
PaintText(g, Bounds, Text, BackBrush, ForeBrush, AlignToRight)
End Sub
Private Sub PaintText(ByVal g As Graphics, ByVal TextBounds As
Rectangle, ByVal Text As String, ByVal BackBrush As Brush, ByVal ForeBrush
As Brush, ByVal AlignToRight As Boolean)
Dim Rect As Rectangle = TextBounds
Dim RectF As RectangleF = RectF.op_Implic it(Rect) ' Convert to
RectangleF
Dim Format As StringFormat = New StringFormat
If AlignToRight Then
Format.FormatFl ags = StringFormatFla gs.DirectionRig htToLeft
End If
Select Case Me.Alignment
Case Is = HorizontalAlign ment.Left
Format.Alignmen t = StringAlignment .Near
Case Is = HorizontalAlign ment.Right
Format.Alignmen t = StringAlignment .Far
Case Is = HorizontalAlign ment.Center
Format.Alignmen t = StringAlignment .Center
End Select
Format.FormatFl ags = Format.FormatFl ags Or StringFormatFla gs.NoWrap
g.FillRectangle (Brush:=BackBru sh, Rect:=Rect)
Rect.Offset(0, yMargin)
Rect.Height -= yMargin
g.DrawString(Te xt, Me.DataGridTabl eStyle.DataGrid .Font, ForeBrush,
RectF, Format)
Format.Dispose( )
End Sub
Private Sub ComboChanged(By Val sender As Object, ByVal e As
System.EventArg s) Handles Combo.Selection ChangeCommitted
ColumnStartedEd iting(Combo)
SetColumnValueA tRow(mSource, mRowNum, Combo.SelectedV alue)
End Sub
Private Function LookupDisplayVa lue(ByVal LookupObject As Object) As
String
If LookupObject Is System.DBNull.V alue Then Return NullText
Dim LookupText As String = LookupObject.To String
Dim I As Integer
Dim IMax As Integer = Combo.Items.Cou nt - 1
Dim DT As DataTable = CType(Combo.Dat aSource, DataTable)
For I = 0 To IMax
If DT.Rows(I)(mVal ueMember).ToStr ing = LookupText Then
Return DT.Rows(I)(mDis playMember).ToS tring
End If
Next
Return String.Empty
End Function
End Class

[pmcguire]

Almost. I needed to reverse the order of statements in your ComboChanged event. Otherwise, when I performed the edit, the ComboBox always contained the text of the first value in its Item list. Since my ColumnStyle differs slightly from yours in other places to (namely the Edit Event), you may possibly not observe this behavior. Anyway, for me at least, it should read

Private Sub ComboChanged(By Val sender As Object, ByVal e As System.EventArg s) Handles Combo.Selection ChangeCommitte
SetColumnValueA tRow(_source, _rowNum, Combo.SelectedV alue
ColumnStartedEd iting(Combo
End Su

You had

Private Sub ComboChanged(By Val sender As Object, ByVal e As System.EventArg s) Handles Combo.Selection ChangeCommitte
ColumnStartedEd iting(Combo
SetColumnValueA tRow(_source, _rowNum, Combo.SelectedV alue
End Su

Now it works like a champ. Thanks, Co

Pat