Client Population of ComboBox with Checkboxes is Slow

[Richard]

Hi,

I have had a combobox for a while that has been populated on the client side using a PageMethod and just manually handling the callbacks etc. to loop through the results and add the items using the .add() function on the item list.  This has worked perfectly for me so far but when I try to turn checkboxes on to make it multi-select, it has slowed right down and the add operation now takes 80-100ms per item which is unacceptable since I have 1000+ items to insert into the combobox.  

Is there anything I can look at to make this faster or maybe some alternative option I can look into rather than what I am doing? I briefly just looked into Load-on-Demand but I noticed it doesn't play well (or at all) with checkboxes which is the whole point of what I'm doing.  And I would like to keep using ​javascript to populate the combobox as it keeps the page more responsive than just wrapping controls in updatepanels and doing everything server side.  Plus then the whole page would need rework and I would like to avoid that if possible. Below is the markup for the combobox.  Again the speed was fine before I enabled checkboxes and as soon as I did, the client add operation started to take ~100ms.

<telerik:RadComboBox ID='cboRoad' runat='server' style='width: 300px;' AllowCustomText="true" EnableTextSelection="true" Filter="Contains" MarkFirstMatch="true" MaxHeight="210px" OnClientBlur="onBlur" CheckBoxes="true" Localization-CheckAllString="All Roads" EnableCheckAllItemsCheckBox="true" Localization-AllItemsCheckedString="All Roads">
    <ExpandAnimation Duration="0" />
    <CollapseAnimation Duration="0" />
</telerik:RadComboBox>

[Veselin Tsvetanov]

Hello Richard,

You are right that Load-on-Demand functionality is not supported when using checkboxes on ComboBox items. You can find more information about the reasons both functionalities cannot be used together in the following documentation article.
Could you, please, post the method and the JavaScript code you are using to populate the ComboBox? It will help us reproduce your scenario and test the performance locally.

Regards,
Veselin Tsvetanov
Telerik