Ajax client-side framework failed to load Asp.Net 4.0

Question

Hi Geniuses

I got a complicated problem with ASP.Net 4.0 Ajax....I started a website with Visual Studio 2010 on my machine,and added some update panels they used to work fine,but suddenly i got that series of errors when i run my website

Microsoft JScript runtime error: ASP.NET Ajax client-side framework failed to load.

Microsoft JScript runtime error: 'Sys' is undefined

The strange things is that i made a website on the same machine with VS 2010 and the update panels there work perfectly.i took its web.config to my new website and changed just the connection..and i got the same error

I tried to search for a solution but i failed to find any real solution.Can anyone help?

Answer 1

This is a common error that happens when you try to call framework javascript function before page have even loaded them.

So ether run your code when dom is ready (eg pageload), ether place your code after the scriptmanager tag, or check to place it after the javascript load from scriptmanager.

Answer 2

Here is the answer by zhughes from this thread on asp.net forum.

The Reason : the path of the javascript generated by the scriptmanager changes when the URL Routing module is used.

The Solution : Tell the routing API to not route the files with "axd" extension (the files generated by the scriptmanager)

Add this rule to the method where you register the routing rules in Global.asax

 routes.Ignore("{resource}.axd/{*pathInfo}");

in addition you should have this section in web.config

<system.webServer>
    <modules runAllManagedModulesForAllRequests="true" />
</system.webServer>

Answer 3

I had this problem and sought an answer from the almighty Google, tried various suggestions including the ones above but had no luck. Gave up and moved on to other work, came back a few days later and the problem had disappeared.

I resumed work, made some code changes and published my website and the problem reappeared. Went back to the Google and came across someone who had the problem while using the 3.5 framework. In that case s/he was able to resolve the problem by going to the 'Add/Remove Programs' control panel and selecting the repair option.

I did likewise, repairing the 'MS .NET Framework 4 Client Profile' and 'MS .NET Framework 4 Extended'. That fixed the problem for me.

Hope that solves it for someone else.