FIX: Items loaded on demand can be added multiple times on scroll (Q3 2009 issue)

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  1. Answer
    Telerik Admin
    Telerik Admin avatar
    1696 posts
    Member since:
    Oct 2004

    Posted 05 Nov 2009 Link to this post

    Hi guys,

    We introduced a small problem in the Q3 2009 (2009.3.1103) in the load on demand mechanism.

    Who is affected:
    All scenarios where:
    EnableLoadOnDemand = True and
    or ShowMoreResults properties are not set to True (it is False by default).

    If there is a scrollbar on the dropdown and you scroll to the bottom of the items list - another request is send to the server and the items are loaded again thus multiplying the items.

    There are several easy workarounds (choose one of them):

    1. Set the _virtualScroll private member of the combobox to false. This can be done in the OnClientLoad event of the combobox:

    function onClientLoadHandler(sender, e) { 
        sender._virtualScroll = false

    2. Set the EndOfItems property to True.
    • In ItemsRequested event this property is a member of the RadComboBoxItemsRequestedEventArgs class:
    protected void RadComboBox1_ItemsRequested(object sender, RadComboBoxItemsRequestedEventArgs e) 
        DataTable data = GetData(e.Text); 
        // ... 
        e.EndOfItems = true

    • In PageMethods mode this property is a member of the RadComboBoxData class:

    public static RadComboBoxData GetCompanyNames(RadComboBoxContext context) 
        DataTable data = GetData(context.Text);          
        RadComboBoxData comboData = new RadComboBoxData(); 
        // ... 
        comboData.Items = result.ToArray(); 
        comboData.EndOfItems = true
        return comboData; 

    • In WebService mode this property is a member of the RadComboBoxData class:
    public RadComboBoxData GetCompanyNames(RadComboBoxContext context) 
        RadComboBoxData comboData = new RadComboBoxData(); 
        // ... 
        comboData.Items = result.ToArray(); 
        comboData.EndOfItems = true
        return comboData; 

    What is next
    The problem is already fixed and will be available in the next Latest Internal Build and the first service pack.

    We apologize for the caused inconvenience.
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