Bizarre Grid Behavior

[Philip]

I'm in the process of converting my Componentart grid to Telerik and I encountered this VERY bizarre behavior.

Clicking on any of the command buttons (add a record, edit, refresh) causes the following error:

Sys.WebForms.PageRequestManagerServerErrorException: Object reference not set to an instance of an object.

Here's the weird part...it doesn't do it every time. I can sit on the same page and click the add a record button 20 times and get that error, but on the 21st click, it will work. Same with the edit button...click it 10 times or so and get that error, but the next click and it goes into edit mode.

I've been scratching my head for the last hour and I can't seem to figure it out.

Here's my code...very basic since I'm still converting

                <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
                    <AjaxSettings>
                        <telerik:AjaxSetting AjaxControlID="RadGrid1">
                            <UpdatedControls>
                                <telerik:AjaxUpdatedControl ControlID="RadGrid1" />
                            </UpdatedControls>
                        </telerik:AjaxSetting>
                    </AjaxSettings>
                </telerik:RadAjaxManager>
                <telerik:RadGrid ID="RadGrid1" Skin="Default2006"
                    Width="160"
                    AllowSorting="True"
                    PageSize="10"
                    ShowFooter="True"
                    AllowPaging="True"
                    OnNeedDataSource="RadGrid1_NeedDataSource"
                    OnInsertCommand="RadGrid1_InsertCommand"
                    OnDeleteCommand="RadGrid1_DeleteCommand"
                    OnUpdateCommand="RadGrid1_UpdateCommand"
                    Gridlines="Both"
                    runat="server">
                    <MasterTableView CommandItemDisplay="Top" EditMode="InPlace" DataKeyNames="den_id" Width="100%" HorizontalAlign="NotSet" AutoGenerateColumns="False">
                        <Columns>
                            <telerik:GridBoundColumn UniqueName="den_id" DataField="den_id" Visible="false" />
                            <telerik:GridEditCommandColumn ButtonType="ImageButton" UniqueName="EditCommandColumn">
                                <ItemStyle Width="85" />
                            </telerik:GridEditCommandColumn>
                            <telerik:GridBoundColumn DataField="den_no" HeaderText="Den" UniqueName="den_no">
                                <ItemStyle Width="50" />
                            </telerik:GridBoundColumn>
                            <telerik:GridDropDownColumn UniqueName="den_type_id" DataSourceID="DenTypeDataSource" ListValueField ="den_type_id" ListTextField="den_type_nm" HeaderText="Den Type" DataField="den_type_id">
                                <ItemStyle Width="100" />
                            </telerik:GridDropDownColumn>
                            <telerik:GridBoundColumn DataField="den_nm" HeaderText="Den Name" UniqueName="den_nm">
                                <ItemStyle Width="150" />
                            </telerik:GridBoundColumn>
                            <telerik:GridDropDownColumn UniqueName="den_ldr_id" DataSourceID="DenLeaderDataSource" ListValueField ="adult_id" ListTextField="adult_nm" HeaderText="Den Leader" DataField="den_ldr_id">
                                <ItemStyle Width="100" />
                            </telerik:GridDropDownColumn>
                            <telerik:GridButtonColumn UniqueName="DeleteColumn" ConfirmText="Delete Den?" ButtonType="ImageButton" CommandName="Delete" >
                                <ItemStyle Width="30" />
                            </telerik:GridButtonColumn>
                        </Columns>
                    </MasterTableView>
                    <PagerStyle Mode="NextPrevAndNumeric" />
                </telerik:RadGrid>
                <asp:SqlDataSource ID="DenTypeDataSource" runat="server" />
                <asp:SqlDataSource ID="DenLeaderDataSource" runat="server" />

here's the code-behind

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        PageTitle.InnerText = "Scout Central-Manage Dens"
        DenTypeDataSource.ConnectionString = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
        DenTypeDataSource.SelectCommand = "SELECT [sc_den_type].[den_type_id], [sc_den_type].[den_type_nm] FROM [sc_den_type] WHERE [sc_den_type].[unit_type_id] = " & Profile.UnitTypeID + " ORDER BY [sc_den_type].[den_type_id] ASC"
        DenLeaderDataSource.ConnectionString = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
        DenLeaderDataSource.SelectCommand = "SELECT [sc_adult].[adult_id], [sc_adult].[adult_fnm] + ' ' + [sc_adult].[adult_lnm] AS [adult_nm] FROM [sc_adult] WHERE [sc_adult].[unit_id] = " & Profile.UnitID
    End Sub

    Protected Sub RadGrid1_NeedDataSource(ByVal source As Object, ByVal e As GridNeedDataSourceEventArgs) Handles RadGrid1.NeedDataSource
        RadGrid1.DataSource = GetDataTable("SELECT [sc_den].[den_id], [sc_den].[den_no], [sc_den].[den_type_id], [sc_den].[den_nm], [sc_den].[den_ldr_id] FROM [sc_den] WHERE [sc_den].[unit_id]=" & Profile.UnitID & " ORDER BY [sc_den].[den_no] ASC")
    End Sub

    Public Function GetDataTable(ByVal query As String) As DataTable
        Dim connstr = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
        Dim dbconn As New SqlConnection(connstr)
        Dim dbadapter As New SqlDataAdapter(query, dbconn)
        Dim oTable1 As New DataTable("Dens")
        Try
            dbadapter.Fill(oTable1)
        Finally
            dbconn.Close()
        End Try
        Return oTable1
    End Function

    Protected Sub RadGrid1_InsertCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs)
        'Get the GridEditFormInsertItem of the RadGrid
        Dim item As GridEditableItem = DirectCast(e.Item, GridEditableItem)

        Dim sql As String = ""
        Dim den_no As String = (TryCast(item("den_no").Controls(0), TextBox)).Text
        Dim den_type_id As String = (TryCast(item("den_type_id").Controls(0), RadComboBox)).SelectedItem.Value
        Dim den_nm As String = (TryCast(item("den_nm").Controls(0), TextBox)).Text
        Dim den_ldr_id As String = (TryCast(item("den_ldr_id").Controls(0), RadComboBox)).SelectedItem.Value

        sql = "INSERT INTO [sc_den] ([unit_id], [den_type_id], [den_no], [den_nm], [den_ldr_id]) VALUES ("
        sql += Profile.UnitID + ", "
        sql += "'" + den_type_id + "', "
        sql += "'" + den_no + "', "
        sql += "'" + den_nm + "', "
        sql += "'" + den_ldr_id + "') "

        Try
            Dim connstr = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
            Dim dbconn As New SqlConnection(connstr)
            dbconn.Open()
            Dim cmd As New SqlCommand(sql, dbconn)
            cmd.ExecuteNonQuery()
            dbconn.Close()
        Catch ex As Exception
            RadGrid1.Controls.Add(New LiteralControl("Unable to add Den. Reason: " + ex.Message))
            e.Canceled = True
        End Try

    End Sub

    Protected Sub RadGrid1_DeleteCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs)
        'Get the GridDataItem of the RadGrid
        Dim item As GridDataItem = DirectCast(e.Item, GridDataItem)

        'Get the primary key value using the DataKeyValue.
        Dim sql As String = ""
        Dim den_id As String = item.OwnerTableView.DataKeyValues(item.ItemIndex)("den_id").ToString()
        sql = "DELETE FROM [sc_den] WHERE [den_id]=" + den_id + " "

        Try
            Dim connstr = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
            Dim dbconn As New SqlConnection(connstr)
            dbconn.Open()
            Dim cmd As New SqlCommand(sql, dbconn)
            cmd.ExecuteNonQuery()
            dbconn.Close()
        Catch ex As Exception
            RadGrid1.Controls.Add(New LiteralControl("Unable to delete Den. Reason: " + ex.Message))
            e.Canceled = True
        End Try

    End Sub

    Protected Sub RadGrid1_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs)
        'Get the GridEditableItem of the RadGrid
        Dim item As GridEditableItem = TryCast(e.Item, GridEditableItem)

        'Get the primary key value using the DataKeyValue.
        Dim sql As String = ""
        Dim den_id As String = item.OwnerTableView.DataKeyValues(item.ItemIndex)("den_id").ToString()
        Dim den_no As String = (TryCast(item("den_no").Controls(0), TextBox)).Text
        Dim den_type_id As String = (TryCast(item("den_type_id").Controls(0), RadComboBox)).SelectedItem.Value
        Dim den_nm As String = (TryCast(item("den_nm").Controls(0), TextBox)).Text
        Dim den_ldr_id As String = (TryCast(item("den_ldr_id").Controls(0), RadComboBox)).SelectedItem.Value
        sql = "UPDATE [sc_den] SET "
        sql += "[den_no]='" + den_no + "', "
        sql += "[den_type_id]='" + den_type_id + "', "
        sql += "[den_nm]='" + den_nm + "', "
        sql += "[den_ldr_id]='" + den_ldr_id + "' "
        sql += "WHERE [den_id]=" + den_id + " "

        Try
            Dim connstr = ConfigurationManager.ConnectionStrings("LocalSqlServer").ToString
            Dim dbconn As New SqlConnection(connstr)
            dbconn.Open()
            Dim cmd As New SqlCommand(sql, dbconn)
            cmd.ExecuteNonQuery()
            dbconn.Close()
        Catch ex As Exception
            RadGrid1.Controls.Add(New LiteralControl("Unable to update Den. Reason: " + ex.Message))
            e.Canceled = True
        End Try

    End Sub

Any ideas on what could be causing this strange behavior?

[Vlad]

Hi Philip,

When you ajaxify the grid using RadAjaxManager "Prometheus" the PageRequestManager will handle all server-side exceptions. If you set EnableAjax="false" for RadAjaxManager you will able to see the exception in normal ASP.NET way where you can check the exception stack trace.

All the best,
Vlad
the Telerik team

Instantly find answers to your questions at the new Telerik Support Center

[Philip]

Well...I still have the behavior that sometimes it works and sometimes it doesn't, now I just get a full stack trace when it doesn't work. Here it is:

[NullReferenceException: Object reference not set to an instance of an object.]
   ComponentArt.Web.UI.Grid.GenerateItems(GridItemCollection arItems, Int32 iLevel) +456
   ComponentArt.Web.UI.Grid.GenerateStorage(GridItemCollection arItems, Int32 iLevel) +62
   ComponentArt.Web.UI.Grid.ComponentArtRender(HtmlTextWriter output) +3933
   ComponentArt.Web.UI.WebControl.Render(HtmlTextWriter output) +48
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20
   System.Web.UI.Control.Render(HtmlTextWriter writer) +7
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +59
   System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +68
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121
   System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +37
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20
   System.Web.UI.Control.Render(HtmlTextWriter writer) +7
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20
   System.Web.UI.Page.Render(HtmlTextWriter writer) +26
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2558

Does that give you any idea why it might throw this error sometimes, but not all the time?

[Philip]

OMG...I'm an idiot.

It was conflicting with the ComponentArt grid that I still had in there for reference. I noticed the stack trace was throwing the error on the ComponentArt grid, not the RadGrid. I removed the CA grid and everything works fine. Well...just another reason to dump CA :) hahaha