Extender Provider failed to return an Extender

We upgraded from .NET 2.0 to .NET 3.5. A co-worker of mine is getting the following dialog when attempting to run the ASP .NET web project under the debugger in Visual Studio 2008. He can build fine, but he can't debug (hence, it's a run-time issue):

Microsoft Visual Studio

"The Extender Provider failed to return an Extender for this object. Please correct before proceeding. (You might rename the current web.config and add a new one.)"

OK

Searching on this error provided one hit that is in French, but Google translated, and the dude deleted his web.config. Well, my co-worker has a web.config.

Thanks!

Solution 1:

I encountered the

The Extender Provider failed to return an Extender for this object.

message in a winforms designer window.

I'm aware that your question is about ASP.Net 3.5, but in my case I resolved it by:

• Closing the solution in Visual Studio
• Deleting the obj and bin directories from the problematic project.

When I reopened the solution the error no longer occurred in the designer.

UPDATE:

VS 2019, resolution still relevant

Solution 2:

I solved it by just closing Visual Studio and opening it again. I was using Visual Studio 2015 Community Edition and didn't have to delete those folders.