"asp.net ajax client-side framework failed to load"
Many of you must have seen this error on some occasions or the other. While there are many posts if u google regarding this error, saying different things. For me it was a strange situation, so the solution provided in this post might be or might not be applicable in your case. But it's worthwhile to give it a go as there is a reason why this error came up in my situation.
Little bit of background: I had this web app running on my VM. Project was created using VS 2008 and VM was having upto .Net 3.5. And the ajaxcontroltoolkit.dll was in the bin folder.
Now I moved this visual studio solution into my home server having VS 2008 and .Net 3.5 SP1. Everything running fine on home server.
Next day I had to take the solution back into my VM on work machine. So copied the solution, opened it and hit F5 (to run the web app!). And what is see on my face is "asp.net ajax client-side framework failed to load".
I tried looking for various solutions by googling it. But none of the solutions made sense to me or didn't fit my situation. Then I thought of leaving the google aside and stressed my mind trying to find the differences. Offcourse .Net 3.5 SP 1 was not available on my VM, but then why should it effect ajaxcontroltoolkit assembly? Still trying to go with gut feeling, I applied .Net 3.5 SP 1 on my VM and saw that the error ranaway.
Now my web app runs fine and the ajax controls were loading fine. Apparently the assembly was JiTed on my home server with SP1 updates which I have to bring to same state on my VM.
Another option you could also try is to repair your .Net 3.5 or .Net 3.5 SP1.