asp net ajax client side framework failed to load

Question

I understand this question has been asked a million times and I have searched everywhere for a fix but nothing suggested worked and I keep getting this error.

I have correct version of AJAX Control Toolkit (version 16.1.1.0, runtime version v4.0.30319); application is .Net Framework 4.0. It build with no errors, I can publish it and access it through localhost but if I need to debug the application and run it from within VS 2013, I keep getting the above error, followed by a couple of "sys is undefined".

When I do View Source, I see a bunch of:

<script src="/WebResource.axd?d=xxxxxxx /script>

followed by:

<script src="../Scripts/WebForms/MsAjax/MicrosoftAjax.js" type="text/javascript"></script>
<script type="text/javascript">
    //<![CDATA[
    if (typeof(Sys) === 'undefined') throw new Error('ASP.NET Ajax client-   side framework failed to load.');
    //]]>
</script>
<script src="../Scripts/WebForms/MsAjax/MicrosoftAjaxWebForms.js" type="text/javascript"></script>
<script src="/ScriptResource.axd?d=xxxxx  ></script> (a bunch of these)
<script type="text/javascript">
    //<![CDATA[
Sys.WebForms.PageRequestManager._initialize('ctl00$ScriptManager1', 'aspnetForm', ['tctl00$upnlProgInfo','','tctl00$MainContent$upnlPopup','','tctl00$MainContent$upnlAI',''], [], [], 90, 'ctl00');
    //]]>
</script> (this is where it throws "sys is undefined)

If I clear browser cache, the first page opens with no error but any subsequent postback starts the same sequence of errors again.

I tried copying web.config from other projects that work (from other application servers; this is the only application on this development server), followed all the modifications suggested when I googled the issue the whole day but nothing is helping. I will attempt to re-install VS 2013 as last resort but appreciate any hints or suggestions.

score 0 · Answer 1 · answered Feb 08 '17 at 12:38

I had tried all the web.config modifications that were recommended, including http handlers, and nothing worked for me. I removed a reference to AspNet.ScriptManager.bootstrap and the issue went away. I have no explanation for this, maybe some guru can shed some light.

asp net ajax client side framework failed to load

1 Answers1