DataGridView column of arbitrary controls per row (or replicate that appearance) - vb.net

Question

I have a DataGridView which contains, among other things, a "Feature" column and a "Value" column. The "Feature" column is a DataGridViewComboBoxColumn. What I would like to do, is manipulate the "Value" column, such that it can be one of a number of controls, depending on the item selected in the "Feature" column on any given row. So, for example :
Feature
Value Cell Behaviour
A
Combobox with a pre-determined set of options, specific to Feature A
B
Combobox with a different set of pre-determined options, specific to Feature B
C
Checkbox
D
Textbox (free-format)
X
etc. etc.
My initial naive approach to this (which I never really expected to work but figured I'd try anyway...) was to programmatically manipulate the specific value cell in the grid whenever the Feature combobox on the same row was changed :
Private Sub dgv_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles dgv.CellValueChanged
Dim changedCell As DataGridViewCell = CType(dgv.Rows(e.RowIndex).Cells(e.ColumnIndex), DataGridViewCell)
If changedCell.ColumnIndex = cboFeatureColumn.Index Then
Dim cboChangedFeature = CType(changedCell, DataGridViewComboBoxCell)
If cboChangedFeature.Value IsNot Nothing Then ConfigureValueField(cboChangedFeature)
End If
End Sub
Private Sub ConfigureValueField(cboFeature As DataGridViewComboBoxCell)
Dim cllValueField As DataGridViewCell = dgv.Rows(cboFeature.RowIndex).Cells(valueColumn.Index)
Dim featureID As Integer = dgv.Rows(cboFeature.RowIndex).Cells(featureIDColumn.Index).Value
Dim matches = From row In dtbFeatureList Let lookupID = row.Field(Of Integer)("ID") Where lookupID = featureID
Dim strFieldControl As String = ""
If matches.Any Then strFeatureControl = matches.First().row.Field(Of String)("FieldControl")
Select Case strFieldControl
Case "Checkbox"
' Do something
Case "Textbox"
' Do something
Case "Combobox"
Dim cboConfigured As New DataGridViewComboBoxCell
Dim dvOptions As New DataView(dtbFeatureValueList)
dvOptions.RowFilter = "[FeatureID] = " & featureID
Dim dtbOptions As DataTable
dtbOptions = dvOptions.ToTable
With cboConfigured
.DataSource = dtbOptions
.ValueMember = "Value"
.DisplayMember = "ValueText"
.DisplayStyle = DataGridViewComboBoxDisplayStyle.ComboBox
.ReadOnly = False
End With
cllValueField = cboConfigured
End Select
End Sub
But this (probably, obviously to many) doesn't work; for starters it throws a DataError Default Error Dialog :
The following exception occurred in the DataGridView:
System.FormatException: DataGridViewComboBoxCell value is not valid To
replace this default dialog please handle the DataError event.
...which I can trap and handle (i.e. ignore!) easily enough :
Private Sub dgv_DataError(sender As Object, e As DataGridViewDataErrorEventArgs) Handles dgv.DataError
e.Cancel = True
End Sub
...and the resulting cell does have the appearance of a combobox but nothing happens when I click the dropdown (no list options appear) I suspect there are a whole host of DataErrors being thrown; to be quite honest, I'm not entirely comfortable with ignoring exceptions like this without handling them properly...
The only alternative option I can think of is to add separate columns for each possible value type (so add a DataGridViewComboBoxColumn for combos, a DataGridViewCheckBoxColumn for checkboxes, a DataGridViewTextBoxColumn for textboxes etc.) but then all of my values are scattered across multiple columns instead of all under a single heading which will be really confusing to look at.
And I really want to retain the appearance of comboboxes (set list of options) versus checkboxes (boolean values) versus textboxes (free-format text), as it makes it a lot easier for users to differentiate the values.
I read somewhere that it may be possible to derive my own custom column class, inheriting the native DataGridViewColumn class, but I couldn't find any examples of how this was done. I've done something similar with a customised DataGridViewButtonColumn but literally just to change the appearance of the buttons across the entire column, not the functionality of the individual cells within it.
Would anybody have any suggestions as to how it might be possible to have a mix of controls in the same column, configured specifically to the row in which they reside?
EDIT
So, I followed the walkthrough at : https://learn.microsoft.com/en-us/dotnet/desktop/winforms/controls/how-to-host-controls-in-windows-forms-datagridview-cells?view=netframeworkdesktop-4.8&redirectedfrom=MSDN
And I've added four new classes to my project as follows :
UserControl class : a basic control which contains a textbox, a combobox and a checkbox, and basic methods for showing/hiding each one as appropriate, configuring the combobox if necessary etc. By default, the UserControl should display as an empty textbox.
CustomConfigurableCellEditingControl : derived from the UserControl in #1
DataGridViewCustomConfigurableCell : container for the EditingControl in #2 and derived from DataGridViewTextBoxCell
DataGridViewCustomConfigurableColumn : container for the Cell in #3 and derived from DataGridViewColumn
Public Class UserControl
Private displayControl As String
Private displayValue As String
Private myValue As String
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
displayControl = "Textbox"
displayValue = ""
refreshDisplay()
End Sub
Public Property ControlToDisplay As String
Get
Return displayControl
End Get
Set(value As String)
displayControl = value
End Set
End Property
Public Property ValueToDisplay As String
Get
Return displayValue
End Get
Set(value As String)
displayValue = value
End Set
End Property
Public Property Value As String
Get
Return myValue
End Get
Set(value As String)
myValue = value
End Set
End Property
Public Sub refreshDisplay()
Select Case displayControl
Case "Textbox"
With ucTextBox
.Text = displayValue
.Visible = True
End With
ucComboBox.Visible = False
ucCheckbox.Visible = False
Case "Combobox"
With ucComboBox
.Visible = True
End With
ucTextBox.Visible = False
ucCheckbox.Visible = False
Case "Checkbox"
With ucCheckbox
.Checked = myValue
.Visible = True
End With
ucTextBox.Visible = False
ucComboBox.Visible = False
End Select
End Sub
Public Sub configureCombobox(dtb As DataTable, valueMember As String, displayMember As String, style As ComboBoxStyle)
With ucComboBox
.DataSource = dtb
.ValueMember = "ID"
.DisplayMember = "FriendlyName"
.DropDownStyle = style
End With
End Sub
End Class
Class CustomConfigurableCellEditingControl
Inherits UserControl
Implements IDataGridViewEditingControl
Private dataGridViewControl As DataGridView
Private valueIsChanged As Boolean = False
Private rowIndexNum As Integer
Public Sub New()
End Sub
Public Property EditingControlFormattedValue() As Object _
Implements IDataGridViewEditingControl.EditingControlFormattedValue
Get
'Return Me.Value.ToShortDateString()
Return Me.valueIsChanged.ToString
End Get
Set(ByVal value As Object)
Me.Value = value
End Set
End Property
Public Function GetEditingControlFormattedValue(ByVal context As DataGridViewDataErrorContexts) As Object _
Implements IDataGridViewEditingControl.GetEditingControlFormattedValue
Return Me.valueIsChanged.ToString
End Function
Public Sub ApplyCellStyleToEditingControl(ByVal dataGridViewCellStyle As DataGridViewCellStyle) _
Implements IDataGridViewEditingControl.ApplyCellStyleToEditingControl
Me.Font = dataGridViewCellStyle.Font
End Sub
Public Property EditingControlRowIndex() As Integer _
Implements IDataGridViewEditingControl.EditingControlRowIndex
Get
Return rowIndexNum
End Get
Set(ByVal value As Integer)
rowIndexNum = value
End Set
End Property
Public Function EditingControlWantsInputKey(ByVal key As Keys,
ByVal dataGridViewWantsInputKey As Boolean) As Boolean _
Implements IDataGridViewEditingControl.EditingControlWantsInputKey
End Function
Public Sub PrepareEditingControlForEdit(ByVal selectAll As Boolean) _
Implements IDataGridViewEditingControl.PrepareEditingControlForEdit
' No preparation needs to be done.
End Sub
Public ReadOnly Property RepositionEditingControlOnValueChange() As Boolean _
Implements IDataGridViewEditingControl.RepositionEditingControlOnValueChange
Get
Return False
End Get
End Property
Public Property EditingControlDataGridView() As DataGridView _
Implements IDataGridViewEditingControl.EditingControlDataGridView
Get
Return dataGridViewControl
End Get
Set(ByVal value As DataGridView)
dataGridViewControl = value
End Set
End Property
Public Property EditingControlValueChanged() As Boolean _
Implements IDataGridViewEditingControl.EditingControlValueChanged
Get
Return valueIsChanged
End Get
Set(ByVal value As Boolean)
valueIsChanged = value
End Set
End Property
Public ReadOnly Property EditingControlCursor() As Cursor _
Implements IDataGridViewEditingControl.EditingPanelCursor
Get
Return MyBase.Cursor
End Get
End Property
Protected Overrides Sub OnValueChanged(ByVal eventargs As EventArgs)
' Notify the DataGridView that the contents of the cell have changed.
valueIsChanged = True
Me.EditingControlDataGridView.NotifyCurrentCellDirty(True)
MyBase.OnValueChanged(eventargs)
End Sub
End Class
Public Class DataGridViewCustomConfigurableCell
Inherits DataGridViewTextBoxCell
Public Sub New()
End Sub
Public Overrides Sub InitializeEditingControl(ByVal rowIndex As Integer,
ByVal initialFormattedValue As Object,
ByVal dataGridViewCellStyle As DataGridViewCellStyle)
' Set the value of the editing control to the current cell value.
MyBase.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle)
Dim ctl As CustomConfigurableCellEditingControl = CType(DataGridView.EditingControl, CustomConfigurableCellEditingControl)
' Use the default row value when Value property is null.
If (Me.Value Is Nothing) Then
ctl.Value = CType(Me.DefaultNewRowValue, String)
Else
ctl.Value = CType(Me.Value, String)
End If
End Sub
Public Overrides ReadOnly Property EditType() As Type
Get
' Return the type of the editing control that Cell uses.
Return GetType(CustomConfigurableCellEditingControl)
End Get
End Property
Public Overrides ReadOnly Property ValueType() As Type
Get
' Return the type of the value that Cell contains.
Return GetType(String)
End Get
End Property
Public Overrides ReadOnly Property DefaultNewRowValue() As Object
Get
Return ""
End Get
End Property
End Class
Imports System.Windows.Forms
Public Class DataGridViewCustomConfigurableColumn
Inherits DataGridViewColumn
Public Sub New()
MyBase.New(New DataGridViewCustomConfigurableCell())
End Sub
Public Overrides Property CellTemplate() As DataGridViewCell
Get
Return MyBase.CellTemplate
End Get
Set(ByVal value As DataGridViewCell)
' Ensure that the cell used for the template is a Custom Configurable Cell.
If (value IsNot Nothing) AndAlso Not value.GetType().IsAssignableFrom(GetType(DataGridViewCustomConfigurableCell)) Then
Throw New InvalidCastException("Must be a Custom Configurable Cell")
End If
MyBase.CellTemplate = value
End Set
End Property
End Class
But... I'm still none the wiser as to how I populate, display, manipulate etc. The code compiles fine, but I just get a blank column. I can't see any controls, I can't see any values and I can't seem to "trap" any of the events that should manipulate them?
With dgv
cfgValueColumn = New DataGridViewCustomConfigurableColumn With {.DisplayIndex = valueColumn.Index + 1}
With cfgValueColumn
.HeaderText = "Custom Value"
.Width = 300
End With
.Columns.Add(cfgValueColumn)
Dim cfgCell As DataGridViewCustomConfigurableCell
For Each row As DataGridViewRow In .Rows
cfgCell = CType(row.Cells(cfgValueColumn.Index), DataGridViewCustomConfigurableCell)
With cfgCell
.Value = row.Cells(valueColumn.Index).Value
End With
Next
End With

Answer 1

Your main approach is correct if you just need to change the type of the given cell based on the ComboBox selection.
When the value changes of the ComboBox cell:
Dispose of the current cell of the target column.
Create a new cell whose type is defined by the ComboBox selection.
Assign the new cell to the grid place of the old one.
Here's a working example.
Private Sub dgv_CellValueChanged(
sender As Object,
e As DataGridViewCellEventArgs) Handles dgv.CellValueChanged
If e.RowIndex < 0 Then Return
If e.ColumnIndex = dgvcTypeSelector.Index Then
Dim cmb = DirectCast(dgv(e.ColumnIndex, e.RowIndex), DataGridViewComboBoxCell)
Dim selItem = cmb.FormattedValue.ToString()
Dim valSelCell = dgv(dgvcValueSelector.Index, e.RowIndex)
valSelCell.Dispose()
Select Case selItem
Case "Text"
valSelCell = New DataGridViewTextBoxCell With {
.Value = "Initial value If any."
}
Case "Combo"
valSelCell = New DataGridViewComboBoxCell With {
.ValueMember = "Value",
.DisplayMember = "ValueText",
.DataSource = dt,
.Value = 2 ' Optional...
}
Case "Check"
valSelCell = New DataGridViewCheckBoxCell With {
.ValueType = GetType(String),
.Value = True
}
valSelCell.Style.Alignment = DataGridViewContentAlignment.MiddleCenter
Case "Button"
valSelCell = New DataGridViewButtonCell With {
.Value = "Click Me!"
}
valSelCell.Style.Alignment = DataGridViewContentAlignment.MiddleCenter
End Select
dgv(dgvcValueSelector.Index, e.RowIndex) = valSelCell
ElseIf e.ColumnIndex = dgvcValueSelector.Index Then
Dim cell = dgv(e.ColumnIndex, e.RowIndex)
Console.WriteLine($"{cell.Value} - {cell.FormattedValue}")
End If
End Sub
Private Sub dgv_CurrentCellDirtyStateChanged(
sender As Object,
e As EventArgs) Handles dgv.CurrentCellDirtyStateChanged
If dgv.IsCurrentCellDirty Then
dgv.CommitEdit(DataGridViewDataErrorContexts.Commit)
End If
End Sub
' If you need to handle the Button cells.
Private Sub dgv_CellContentClick(
sender As Object,
e As DataGridViewCellEventArgs) Handles dgv.CellContentClick
If e.RowIndex >= 0 AndAlso
e.ColumnIndex = dgvcValueSelector.Index Then
Dim btn = TryCast(dgv(e.ColumnIndex, e.RowIndex), DataGridViewButtonCell)
If btn IsNot Nothing Then
Console.WriteLine(btn.FormattedValue)
End If
End If
End Sub
Note, I've changed the value type of the check box cell by ValueType = GetType(String) to avoid throwing exceptions caused by the different value types of the check box and main columns. I'd assume the main column here is of type DataGridViewTextBoxColumn. So you have String vs. Boolean types. If you face problems in the data binding scenarios, then just swallow the exception.
Private Sub dgv_DataError(
sender As Object,
e As DataGridViewDataErrorEventArgs) Handles dgv.DataError
If e.RowIndex >= 0 AndAlso e.ColumnIndex = dgvcValueSelector.Index Then
e.ThrowException = False
End If
End Sub