GridDropDownColumns blank on postback

3 posts, 0 answers
  1. Paul Taylor
    Paul Taylor avatar
    41 posts
    Member since:
    Jun 2010

    Posted 10 May 2011 Link to this post

    I have a RadGrid with several GridDropDownColumns configured as well as several GridBoundColumns. The grid is bound to a data source programatically using the NeedDataSource event. The dropdown columns use RadComboBox style drop downs which are also bound to datasources programatically, in the grid's ItemDataBound event when the grid is in Edit mode. When the grid is not in Edit mode, I set the value of the dropdown column cell's Text property, also in the ItemDataBound event.

    This all works are required. However if I do something that causes a postback, but does not rebind the grid when the grid is not in Edit mode - for example selecting a row in the grid - the values in the dropdown columns go blank. Is the TableCell.Text property not persisted through postback? If not, which property should I use for this purpose, or how can I populate it again, given that the ItemDataBound property does not fire which you simply select a row in the grid.

    Code sample below:

    <telerik:RadGrid runat="server" ID="grdControl" AllowFilteringByColumn="True" AllowPaging="True"
        AllowSorting="True" GridLines="None">
        <MasterTableView AutoGenerateColumns="False" EditMode="EditForms" DataKeyNames="ControlId, StepId"
            CommandItemDisplay="Bottom">
            <CommandItemSettings ExportToPdfText="Export to Pdf"></CommandItemSettings>
            <Columns>
                <telerik:GridButtonColumn ButtonType="LinkButton" Text="Select" CommandName="Select" UniqueName="Select">
                </telerik:GridButtonColumn>
                <telerik:GridEditCommandColumn UniqueName="Edit">
                </telerik:GridEditCommandColumn>
                <telerik:GridButtonColumn CommandName="Delete" Text="Delete" UniqueName="Delete">
                </telerik:GridButtonColumn>
                <telerik:GridDropDownColumn DataField="ControlName" HeaderText="Control Type" UniqueName="ControlName">
                </telerik:GridDropDownColumn>
                <telerik:GridBoundColumn DataField="MaxLength" HeaderText="Max Length" UniqueName="MaxLength">
                </telerik:GridBoundColumn>
                <telerik:GridDropDownColumn DataField="TextMode" HeaderText="Text Mode"
                    UniqueName="TextMode" />
                <telerik:GridDropDownColumn DataField="ListSource" HeaderText="List Source" UniqueName="ListSource">
                </telerik:GridDropDownColumn>
                <telerik:GridBoundColumn DataField="EmptyListText" HeaderText="Empty List Text" UniqueName="EmptyListText">
                </telerik:GridBoundColumn>
            </Columns>
        </MasterTableView>
        <FilterMenu>
        </FilterMenu>
        <HeaderContextMenu CssClass="GridContextMenu GridContextMenu_Default">
        </HeaderContextMenu>
    </telerik:RadGrid>
     
     
     
            Private Sub grdControl_ItemDataBound(ByVal sender As Object, ByVal e As Telerik.Web.UI.GridItemEventArgs) Handles grdControl.ItemDataBound
                If TypeOf e.Item Is GridEditableItem Then
                    Dim item As GridEditableItem = e.Item
                    Dim control As FormControlInfo
                    Dim ffc As New FlexFormController()
                    If TypeOf e.Item Is GridEditFormItem AndAlso e.Item.IsInEditMode Then
                        If e.Item.OwnerTableView.IsItemInserted Then
                            control = New FormControlInfo()
                        Else
                            control = e.Item.DataItem
                        End If
                        Dim editor As GridDropDownListColumnEditor
                        Dim cbo As RadComboBox
                        'ControlName dropdown
                        Dim path As String = Server.MapPath("~/DesktopModules/Dotcom.FlexForm/Components/FormControls/")
                        Dim files As String() = IO.Directory.GetFiles(path, "*.ascx")
                        For i = 0 To files.Length - 1
                            files(i) = IO.Path.GetFileName(files(i)).Replace(".ascx", String.Empty)
                        Next
                        editor = item.EditManager.GetColumnEditor("ControlName")
                        editor.DataSource = files
                        editor.DataBind()
                        editor.SelectedValue = control.ControlName
                        'ListSource dropdown
                        editor = item.EditManager.GetColumnEditor("ListSource")
                        Dim controller As New Lists.ListController()
                        Dim list As Lists.ListInfoCollection
                        If String.IsNullOrEmpty(control.ParentKey) Then
                            list = controller.GetListInfoCollection()
                            editor.DataTextField = "DisplayName"
                            editor.DataValueField = "Key"
                        Else
                            list = controller.GetListInfoCollection(Nothing, control.ParentKey.Replace(":", "."))
                            editor.DataTextField = "Name"
                            editor.DataValueField = "Name"
                        End If
                        editor.DataSource = list
                        editor.DataBind()
                        cbo = editor.ComboBoxControl
                        cbo.Items.Insert(0, New RadComboBoxItem(Localization.GetString("EmptyListItem", Definition.SharedResources), String.Empty))
                        If Not String.IsNullOrEmpty(control.ListSource) Then
                            editor.SelectedValue = control.ListSource
                        End If
                        'TextMode dropdown
                        editor = item.EditManager.GetColumnEditor("TextMode")
                        editor.DataSource = [Enum].GetNames(GetType(TextBoxMode))
                        editor.DataBind()
                        cbo = editor.ComboBoxControl
                        cbo.Items.Insert(0, New RadComboBoxItem(Localization.GetString("EmptyListItem", Definition.SharedResources), String.Empty))
     
                    Else
                        control = e.Item.DataItem
                        item("ControlName").Text = control.ControlName
                        item("ListSource").Text = control.ListSource
                        item("EmptyListText").Text = Server.HtmlEncode(control.EmptyListText)
                        item("ParentControlId").Text = control.ParentId
                        If control.TextMode.HasValue Then
                            item("TextMode").Text = control.TextMode.Value.ToString
                        End If
                    End If
                End If
            End Sub



  2. Marin
    Admin
    Marin avatar
    1045 posts

    Posted 13 May 2011 Link to this post

    Hi Paul,

    Indeed the Text property of the TableCell is not persisted across postback because when you change the value in the ItemDataBound event it is not tracked by the view state. You can either rebind the grid to cause ItemDataBound to fire again or you can manually persist those text values in Session or ViewState, and populate them again on postback in the correct cells. Another option will be if you could bind the GridDropDownColumn in the markup instead of code behind.
     
    Kind regards,
    Marin
    the Telerik team

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  4. Vikas
    Vikas avatar
    4 posts
    Member since:
    Feb 2014

    Posted 03 Mar 2014 Link to this post

    Paul, just wondering if you were able to resolve this issue. If yes, how?

    Thanks,
    Vikas
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