ClientIDMode = “Predictable” broke my dropdown list auto partial postback

In my previous post, I try to upgrade my recent .NET web apps to use recent .NET for capabilities by doing this

<pages controlRenderingCompatibilityVersion="4.0">

But unfortunately, I find couple of my control inside UPDATE PANEL – does not do Partial Postback anymore. (It is doing FULL postback now)

This only happen to a control outside button which I have set as autoPostback = true.





After looking around and test which part that I need to put it back, I found clientIDMode.

I need to set clientIDMode=“AutoID” because the default value is “Predictable”.

<pages controlRenderingCompatibilityVersion="4.0" clientIDMode="Predictable">

The weird things is I try to compare the id and html which generated by both “predictable and “AutoID”. And the result is the SAME but the different is one of them can do partial postback and one of them not.

<!-- Generated when I set "clientIDMode='Predictable'" -->
<select class="ddlPostback" id="ContentPlaceHolderDefault_MainContainerPlaceHolder_ucProductDetail_rptVariationChoiceGroup_ddlChoiceGroup_0" onchange="javascript:setTimeout('__doPostBack(\'ctl00$ctl00$ctl00$ContentPlaceHolderDefault$MainContainerPlaceHolder$ucProductDetail$rptVariationChoiceGroup$ctl00$ddlChoiceGroup\',\'\')', 0)" name="ctl00$ctl00$ctl00$ContentPlaceHolderDefault$MainContainerPlaceHolder$ucProductDetail$rptVariationChoiceGroup$ctl00$ddlChoiceGroup">
        <option value="">Please select</option>
        <option value="2" selected="selected">Green</option>
        <option value="3">Yellow</option>
        <option value="4">Blue</option>
        <option value="5">Brown</option>
</select>
    
    
<!-- Generated when I set "clientIDMode='AutoID'" -->    
<select class="ddlPostback" id="ContentPlaceHolderDefault_MainContainerPlaceHolder_ucProductDetail_rptVariationChoiceGroup_ddlChoiceGroup_0" onchange="javascript:setTimeout('__doPostBack(\'ctl00$ctl00$ctl00$ContentPlaceHolderDefault$MainContainerPlaceHolder$ucProductDetail$rptVariationChoiceGroup$ctl00$ddlChoiceGroup\',\'\')', 0)" name="ctl00$ctl00$ctl00$ContentPlaceHolderDefault$MainContainerPlaceHolder$ucProductDetail$rptVariationChoiceGroup$ctl00$ddlChoiceGroup">
        <option value="">Please select</option>
        <option value="2" selected="selected">Green</option>
        <option value="3">Yellow</option>
        <option value="4">Blue</option>
        <option value="5">Brown</option>
</select>