Problems with OnItemUpdating for DetailsView

My issue is similar to https://www.experts-exchange.com/questions/23004459/Trouble-with-DetailsView-OnItemUpdating.html, but in my case I'm dynamically adding TemplateFields to the DetailsView instead of simple BoundFields.

I'm still working with TextBox controls for now, but when I get this to work I need to be able to use this mechanism with other webcontrols like DropDownList etc. as well.

The textboxes show up fine in the detailsview and display the value from the datasource (= a datatable). But when capturing the newly entered values in OnItemUpdating, the Fields collection is empty and so are e.Keys and e.NewValues .

Partial Public Class wsExtendedDetailsView
    Inherits System.Web.UI.WebControls.DetailsView
 
    Private _oSystem As New wsSystem
    Private _oDP As New wsDataProvider
 
#Region "Overrides"
 
    Protected Overrides Sub OnItemCreated(ByVal e As System.EventArgs)
 
        'Be sure to call the base class's OnItemCreated method!
        MyBase.OnItemCreated(e)
 
        If Me.Rows.Count > 0 Then
            ' swap each header <td> cell for a <th> cell
            For Each l_oRow As DetailsViewRow In Me.Rows
                If l_oRow.RowType = DataControlRowType.DataRow Then
                    Dim l_oTD As DataControlFieldCell = l_oRow.Cells(0)
                    If l_oTD.Controls.Count = 0 Then
                        Dim l_oTH As DataControlFieldHeaderCell = New DataControlFieldHeaderCell(l_oTD.ContainingField)
                        l_oTH.Text = l_oTD.Text
                        l_oTH.Attributes.Add("scope", "row")
 
                        ' add the new th and remove the old td
                        l_oRow.Cells.RemoveAt(0)
                        l_oRow.Cells.AddAt(0, l_oTH)
                    End If
                End If
            Next
        End If
 
    End Sub
 
    Protected Overrides Function CreateFieldSet(ByVal dataItem As Object, ByVal useDataSource As Boolean) As System.Collections.ICollection
 
        Dim l_aFields As New ArrayList()
        For Each l_oField As DataControlField In MyBase.CreateFieldSet(dataItem, useDataSource)
            l_aFields.Add(l_oField)
        Next
 
        ' we have a predefined set of database columns to display
        For Each l_sColumn As String In Me.DisplayColumns
 
            ' see if the column exists in the database
            If _oDP.IsColumn(Me.PrimaryTable, l_sColumn) Then
 
                ' determine the language specific string to use for HeaderText
                Dim l_sHeader As String = wsLanguage.GetExternalDataForLanguage(Me.PrimaryTable, l_sColumn, "columnname")
                If wsUtils.IsEmpty(l_sHeader) And l_sColumn.ToUpper = "ID" Then
                    l_sHeader = l_sColumn
                End If
 
                ' 
                Dim l_oColumn As New TemplateField()
                l_oColumn.HeaderText = l_sHeader & " : "
                l_oColumn.ItemTemplate = New wsDetailsViewTemplate("literal", l_sColumn)
                If l_sColumn.ToUpper = "ID" Then
                    ' primary key always just a Literal (and thus never editable)
                    l_oColumn.EditItemTemplate = New wsDetailsViewTemplate("literal", l_sColumn)
                    l_oColumn.InsertItemTemplate = New wsDetailsViewTemplate("literal", l_sColumn)
                Else
                    l_oColumn.EditItemTemplate = New wsDetailsViewTemplate("textbox", l_sColumn)
                    l_oColumn.InsertItemTemplate = New wsDetailsViewTemplate("textbox", l_sColumn)
                End If
 
                ' add the new TemplateField to the Fields collection
                l_aFields.Add(l_oColumn)
 
            End If
 
        Next
 
        Return l_aFields
 
    End Function
 
    Protected Overrides Sub OnItemUpdating(ByVal e As System.Web.UI.WebControls.DetailsViewUpdateEventArgs)
 
        Dim l_aColumns As New Hashtable, l_iIndex As Integer = 0
 
        If Me.Fields.Count > 0 Then
 
            For l_iI As Integer = 0 To Me.Rows.Count - 1
                Dim l_oNormal As DataControlFieldCell = Me.Rows(l_iI).Cells(0)
                Me.Fields(l_iI).ExtractValuesFromCell(e.Keys, l_oNormal, DataControlRowState.Normal, True)
                Dim l_oEdit As DataControlFieldCell = Me.Rows(l_iI).Cells(1)
                Me.Fields(l_iI).ExtractValuesFromCell(e.NewValues, l_oEdit, DataControlRowState.Edit, False)
            Next
 
            ' the following is for testing only... these always turn up empty
            For Each l_sKey As String In e.Keys
                Dim l_sKeyValue = e.Keys(l_sKey)
            Next
            For Each l_sKey As String In e.NewValues
                Dim l_sNewValue = e.NewValues(l_sKey)
            Next
 
        End If
 
        'Be sure to call the base class's OnItemUpdating method!
        MyBase.OnItemUpdating(e)
 
    End Sub
 
#End Region
 
#Region "Custom properties (using ViewState)"
...
#End Region
 
End Class
 
==================================================================
 
Public Class wsDetailsViewTemplate
    Implements ITemplate
 
    Dim _sControlType As String
    Dim _sColumnName As String
 
    Sub New(ByVal p_sControlType As String, ByVal p_sColumn As String)
        _sControlType = p_sControlType
        _sColumnName = p_sColumn
    End Sub
 
    Sub InstantiateIn(ByVal p_oContainer As Control) _
        Implements ITemplate.InstantiateIn
 
        Select Case _sControlType.ToLower
            Case "textbox"
                Dim l_oTextBox As New TextBox
                l_oTextBox.ID = _sColumnName
                AddHandler l_oTextBox.DataBinding, AddressOf OnDataBinding
                p_oContainer.Controls.Add(l_oTextBox)
            Case Else
                ' implement Literal as default
                Dim l_oLiteral As New Literal
                l_oLiteral.ID = _sColumnName
                AddHandler l_oLiteral.DataBinding, AddressOf OnDataBinding
                p_oContainer.Controls.Add(l_oLiteral)
        End Select
 
    End Sub
 
    Protected Sub OnDataBinding(ByVal sender As Object, ByVal e As System.EventArgs)
 
        Dim l_oControl As Object, l_oContainer As wsExtendedDetailsView
        Select Case _sControlType.ToLower
            Case "textbox"
                l_oControl = TryCast(sender, TextBox)
                l_oContainer = TryCast(l_oControl.NamingContainer, wsExtendedDetailsView)
                l_oControl.Text = DataBinder.Eval(l_oContainer.DataItem, _sColumnName)
            Case Else
                ' implement Literal as default
                l_oControl = TryCast(sender, Literal)
                l_oContainer = TryCast(l_oControl.NamingContainer, wsExtendedDetailsView)
                l_oControl.Text = DataBinder.Eval(l_oContainer.DataItem, _sColumnName)
        End Select
 
    End Sub
 
End Class

Select allOpen in new window