RadGrid Virtual Scrolling Issue

[Torrey]

Hello,

I have utilized the virtual scrolling example provided by the Telerik website verbatim - with exception to the implemented DataSource (which I'm doing programmatically for the sake of the example), and am getting issues. The website is here: Virtual Scrolling and Paging.

The problems are as follows:

• When I scroll to the bottom of the list, the AJAX request runs properly (seen during debugging), but the grid does not update with more records. Also, all other attempts to scroll cause the loading animation to appear and simply hang on the screen so that the page must be reloaded
• After clicking on either of the heading columns to sort, it's successful the 1st time, but afterwards it hangs, nothing is clickable, and the page must be reloaded

Please see the attached image 'ScrollingHangingIllustration.png'. Also, see below for the code. Please help!!

Client-Side RadCodeBlock

<telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
    <script type="text/javascript">
        function HandleScrolling(e) {
            var grid = $find("<%=RadGrid1.ClientID %>");
          var scrollArea = document.getElementById("<%= RadGrid1.ClientID %>" + "_GridData");
          if (IsScrolledToBottom(scrollArea)) {
              var currentlyDisplayedRecords = grid.get_masterTableView().get_pageSize() * (grid.get_masterTableView().get_currentPageIndex() + 1);
              //if the visible items are less than the entire record count
              //trigger an ajax request to increase them
              if (currentlyDisplayedRecords < 100)
              { $find("<%= RadAjaxManager1.ClientID %>").ajaxRequest("LoadMoreRecords"); }
      }
  }
  //calculate when the scroll bar is at the bottom
  function IsScrolledToBottom(scrollArea) {
      var currentPosition = scrollArea.scrollTop + scrollArea.clientHeight;
      return currentPosition == scrollArea.scrollHeight;
  }
    </script>
  </telerik:RadCodeBlock>

Client-Side AJAX Manager

<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" OnAjaxRequest="RadAjaxManager1_AjaxRequest">
  <AjaxSettings>
    <telerik:AjaxSetting AjaxControlID="RadGrid1">
      <UpdatedControls>
        <telerik:AjaxUpdatedControl ControlID="RadGrid1" LoadingPanelID="RadAjaxLoadingPanel1" />
      </UpdatedControls>
    </telerik:AjaxSetting>
  </AjaxSettings>
</telerik:RadAjaxManager>
<telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server" Height="75px"
  Width="75px" Transparency="25">
  <img alt="Loading..." src='<%= RadAjaxLoadingPanel.GetWebResourceUrl(Page, "Telerik.Web.UI.Skins.Default.Ajax.loading.gif") %>'
    style="border: 0;" /></telerik:RadAjaxLoadingPanel>

Client-Side RadGrid

<telerik:RadGrid ID="RadGrid1" runat="server" Skin="Silk" AllowSorting="True" AllowPaging="True" PageSize="15" Width="97%" AutoGenerateColumns="False" GridLines="None">
  <PagerStyle Visible="False" />
  <MasterTableView Width="99%" TableLayout="Fixed" CommandItemDisplay="None" CurrentResetPageIndexAction="SetPageIndexToFirst" PageSize="15">
      <SortExpressions>
          <telerik:GridSortExpression FieldName="CreateDate" SortOrder="Descending" />
      </SortExpressions>
      <Columns>
          <telerik:GridBoundColumn HeaderText="Code" DataField="ZipFileCode" UniqueName="ZipFileCode">
              <HeaderStyle Width="90px" />
          </telerik:GridBoundColumn>
          <telerik:GridBoundColumn HeaderText="Description" DataField="ZipFileDesc" UniqueName="ZipFileDesc">
          </telerik:GridBoundColumn>
          <telerik:GridBoundColumn HeaderText="Select/Omit" DataField="ZipType" UniqueName="ZipType">
              <HeaderStyle Width="100px" />
          </telerik:GridBoundColumn>
          <telerik:GridBoundColumn HeaderText="Create Date" DataField="CreateDate" UniqueName="CreateDate" DataType="System.DateTime" DataFormatString="{0:d}" ShowSortIcon="true">
              <HeaderStyle Width="100px" />
          </telerik:GridBoundColumn>
          <telerik:GridBoundColumn HeaderText="Company" DataField="Company" UniqueName="Company">
              <HeaderStyle Width="100px" />
          </telerik:GridBoundColumn>
      </Columns>
  </MasterTableView>
  <ClientSettings>
    <Scrolling AllowScroll="True" UseStaticHeaders="True" ScrollHeight="300px" />
    <ClientEvents OnScroll="HandleScrolling" />
  </ClientSettings>
</telerik:RadGrid>

Server-Side AjaxRequest

Protected Sub RadAjaxManager1_AjaxRequest(ByVal sender As Object, ByVal e As AjaxRequestEventArgs) Handles RadAjaxManager1.AjaxRequest
    RadGrid1.PageSize = 10 + RadGrid1.PageSize
    RadGrid1.Rebind()
End Sub

Server-Side Datasource

Public Function GetItemsTest(ByVal startRowIndex As Integer, ByVal maxRows As Integer) As DataSet
    Dim dt As DataTable = New DataTable("Sample")
    dt.Columns.Add("Company", System.Type.GetType("System.String"))
    dt.Columns.Add("ZipFileCode", System.Type.GetType("System.String"))
    dt.Columns.Add("ZipFileDesc", System.Type.GetType("System.String"))
    dt.Columns.Add("ZipType", System.Type.GetType("System.String"))
    dt.Columns.Add("CreateDate", System.Type.GetType("System.DateTime"))
    dt.Columns.Add("DeletedFile", System.Type.GetType("System.Boolean"))
    dt.Columns.Add("UploadedBy", System.Type.GetType("System.String"))

    Dim row As DataRow
    Dim dte As DateTime
    dte = DateTime.Now

    For i As Integer = 0 To maxRows
        row = dt.NewRow()
        row(0) = "Company" & i
        row(1) = "ZipFileCode" & i
        row(2) = "ZipFileDesc" & i
        row(3) = "ZipType" & i
        row(4) = dte
        row(5) = True
        row(6) = "UploadedBy" & i
        dt.Rows.Add(row)
    Next

    Dim ds As New DataSet("Sample")
    ds.Tables.Add(dt)

    Return ds
End Function

Private Sub RadGrid1_NeedDataSource(ByVal source As Object, ByVal e As Telerik.Web.UI.GridNeedDataSourceEventArgs) Handles RadGrid1.NeedDataSource

    RadGrid1.DataSource = GetItemsTest(0, RadGrid1.PageSize)

End Sub

Thanks!