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

Question

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 sudden

Answer 1

It may be simply missing part in your web.config like the <Handlers> of <httpHandlers>, my advice is if you have old copy of your web config try it out.

Answer 2

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

Add reference like this..

<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>              
<add assembly="System.Data.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
<add assembly="System.Data.Services, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
<add assembly="System.Data.Services.Client, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

Answer 3

1. If .Net Framework 4.0 client Profile is not available in your machine , so repair .net Frame work 4.0 or re install .
2. go to Project Property and select target framework 3.5.

Answer 4

I had this problem as well dealing with a master page and in my case it was a "Base" meta setting that was messing me up. I do recall reading another article/blog somewhere where they mentioned an issue with ajax validation across different domains causing this type of error.

So in my case, I had a <base...> reference setting the default url for the site but my dev was obviously a different url...thus conflict and the "ASP.NET Ajax client-side framework failed to load." error.

Removed the base and voila...error gone.

HTH

Dave

Answer 5

I was having the same problem. I installed VS 2010 SP1 and the problem went away.

Answer 6

I have found that this is a possibly a caching/compression issue and by putting in the following into Web.Config, resolves the issue.

<system.web.extensions>
    <scripting>
      <scriptResourceHandler enableCaching="false" enableCompression="false" />
    </scripting>
</system.web.extensions>