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Combo Control Freezes when loading lots of data

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ComboBox
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Ian B
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Ian B asked on 10 Jul 2008, 03:33 PM
I am loading approx. 700 records into a radCombo control. I am using LoadOnDemand to do this, but virtual paging is disabled so all 700 records are loaded in one hit. ShowWhileLoading is set to false and item caching disabled.

When the load occurs, the Loading... message is shown at first. This disappears, some data is displayed but the drop down part of the combo becomes unresponsive. It takes a few seconds for it to respond again. This is a big problem as it appears as if the control has finished loading, so users try to select items from the list or scroll up/down. However nothing happens for a few seconds then all their actions occur at once, resulting in list moving up/down repeatedly, random items being selected etc (depending on what user did whilst control was frozen).

I've tried to hook into the client side events to enable a "please wait" message to be shown. However, the OnClientItemsRequested and OnClientDropDownOpened events fire before the control freezes. There is no way programatically I can detect when the control "comes back to life".

The simplistic answers such as reducing data or paging are not an option. Our business requirements prevent us from being able to use virtual paging, reducing the number of items in the list or enabling item caching.

From my understanding, the control should have finished loading before it is displayed. However, it looks like the rendering of so many items is the cause of the "freeze", not the load of the data. The expected behaviour would be for the rendering to complete first, before the data is displayed. The behaviour at present is seen as a showstopper and may prevent us from using the radCombo control at all. Is it possible that this could be looked at, with regard to getting a hotfix for this?

Thanks.


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Simon
Telerik team
answered on 14 Jul 2008, 01:24 PM
Hi Ian B,

The functionality of RadComboBox is a result of mixing all these various features into a complex  component. Hence the loading time needed  for 700 items to be added to the ComboBox is too long.

Changing this behavior would require a fundamental rewrite of some basic features, which on the other hand would require a serious research.

We can, therefore, suggest that you use the ShowMoreResultsBox mechanism and show only portions of items instead of loading all the items at once. You can read more about this feature here.

For a live example, see Load On Demand
.

Regards,
Simon
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Chris
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answered on 29 Jan 2009, 09:25 PM
Hi, Simon.  Both the links in your reply don't work.  Can you please check them and let me know?  Thanks.

Chris
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Princy
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answered on 30 Jan 2009, 05:35 AM
Hello Christopher,

For information on the ShowMoreResultsBox mechanism, you can refer to the following link :
ShowMoreResultsBox
You can also go through the following online demo which demonstrates on the LoadOnDemand feature of the RadComboBox :
Load On Demand

Thanks
Princy
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Ian B
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Simon
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Chris
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