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ComboBox SelectedIndexChanged event does not fire on first AJAX request

Jason Grovert

Posted on May 14, 2007 (permalink)

We have a Web User Control that dynamically loads other Web User Controls as part of a Wizard style control. One of the User Controls contains a ComboBox that performs a PostBack via AJAX to load data into another ComboBox. When a value is selected the PostBack occurs but the Event does not fire on the first Request. If the value is selected again the Event fires. We have stepped through the code to check for errors or inadvertent calls to DataBind which could cause the event not to fire. Furthermore, we have duplicated this functionality outside of our SiteFinity project using the r.a.d ComboBox and it works correctly. We have also attempted to use a standard ASP.Net DropDownList control to eliminate the possibility of the problem being related to the ComboBox.

We are using the Microsoft AJAX controls and MasterPages on this project. The ScriptManager control is located on the MasterPage. Both the Web User Controls each contain an UpdatePanel.

This issue is preventing us from moving forward on this project.

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Jason Grovert

Posted on May 24, 2007 (permalink)

The reason your sample works is because the r.a.d. ComboBox controls are not being loaded dynamically into your Web User Control. To reproduce the problem you need to replace both of the ComboBox controls with a PlaceHolder control and a Button (or some other control that can initiate the CallBack) and load the ComboBox using the LoadControl() method. Basically the problem amounts to the fact that the control (the ComboBox in this example) is being loaded during the PostBack which is what appears to be causing the problem. The control apparently needs to be loaded when page is first visible (i.e. the initial load or PostaBack == false). If this is not the case please let us know what else could be the cause.

We tried a work around by using the RequestItems client-side method but when we attempt to set the ExternalCallBackPage property it defaults to "/sitefinity" and the root of the path and we cannot override that. We need to be able to set the path as being either relative to root (which "/sitefinity" is not) or absolute. I think this might be a bug with that control.

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Shahzad Ilyas

Posted on Oct 19, 2011 (permalink)

Hi
i had the same problem but i found the solution thanks to Shinu..:D

Quote "One suggestion would be invoking postback from client side SelectionIndexChanged event of RadComboBox instead of setting the AutoPostBack property to True. Give a try with the following code."

ASPX

<telerik:RadComboBox ID="RadComboBox1" runat="server" AutoPostBack="false" AllowCustomText="True" OnSelectedIndexChanged="RadComboBox1_SelectedIndexChanged"

OnClientSelectedIndexChanged="OnClientSelectedIndexChanged">

<Items>

<telerik:RadComboBoxItem runat="server" Text="RadComboBoxItem1" Value="RadComboBoxItem1">

</telerik:RadComboBoxItem>

</Items>

</telerik:RadComboBox>

JavaScript

<script type="text/javascript">

function OnClientSelectedIndexChanged(sender, args)

{

__doPostBack('RadComboBox1','');

}

</script>

thank you so much shinu...
regards
Shaz

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