Extender Provider failed to return an Extender

Question

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!

Misdoubt

Same problem when i right click on a solution folder Add>View. I got around it by clicking New Item instead. – Samora

Having this error in 2019. Also occasionally get "there is an error in your web.config". – Pongee

Answer 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

UPDATE:

VS 2022, resolution still relevant

Westerfield

Sounds good. Thanks for taking the time to answer this question. – Misdoubt

Had the same problem with VS2012 today; this fixed it. Thanks! – Deceive

Same problem when Sharepoint list definitions are shown as normal folders instead of sharepoint list definitions! Thanks for the answer!!! – Avelinaaveline

I got the error in VS2015, for a WPF project. I tried to "Clean" the project, but that also did not work. Then I closed the solution (as Dan suggested), and after reopening I was able to Clean and then Run my project. – Greedy

Same here for VS 2015 with a web project. Clean did not solve the problem, but closing VS and deleting the obj and bin folders worked. – Pohai

This occured to me when deleting language-specific *.resx files from a Form. The solution above worked. – Bryozoan

Restarting the visual studio alone resolves the issues for me. Thanks. – Gravestone

I recently saw this in VS 2019 and was able to solve it by closing VS, deleting the .vs folder, then re-opening the solution. – Montanez

Worked me for me on vs2017 on a solution with two web projects – Onomastic

Worked for me as well, asp.net project in vs2019 – Swivel

Just to add to the order of operations that worked: I deleted the bin and obj directories in the Web service project to no avail then closed and re-opened Visual Studio 2019 and the error disappeared! I encountered this one last when I switched branches to merge in some changes from another branch and then switched back to that branch to run the solution again. – Mashburn

I got the error in vs2022. – Pongee

Nice, VS2019, worked. – Acantho

as I have special items added to 'bin/debug' and 'bin/release', I didn't delete the 'bin' directory, but believe that just wiping the 'obj' directory was enough. Thanks. But yes not sure 'bin' is needed. – Splat

Answer 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.

UPDATE:

Helps with Visual Studio 2022 as well.

Unamerican

Same here, using VS Professional 2019 and was seeing that error while upgrading an MVC project from v4.5.2 to v4.8. Restart solved it. – English

This did the trick for me in Visual Studio 2022. Thanks. – Flabellum

Works here as well in 2022. I wonder when they will fix it. – Pongee

In that case It's Not a Bug, It's a Feature :) – Amieeamiel

Answer 3

In my case run Visual Studio as administrator helped. My project uses local IIS and Studio needs Admin permissions to manage IIS.

Fingerprint

This was the solution for me too, for Visual Studio 2019, none of the others worked. Of course the new VS install didn't carry over the "Run as Administrator" setting on my VS2017 shortcut (which I had set years ago and totally forgotten about) – Plagio

Answer 4

None of the solutions above worked in VS2019 for me. What did work was deleting the ProjectName.csproj.user file and then reloading the project.

Musette

Answer 5

In Visual Studio 2019 I had several webservices in a solution failing to load with this error. In my case the error was caused because I had changed the port numbers in IIS for those web services meaning the port numbers in .csproj and/or csproj.user did not match IIS. As soon as I updated the .csproj port numbers to match IIS, the error went away.

Tupler

Answer 6

VS2019 - restarting Visual Studio did the trick.

Highhat

Answer 7

I had this issue in Visual Studio 2015, the error kept persisting even after cleaning the project, restarting visual studio and restarting my pc.

What resolved it for me, was right-clicking the xaml file and choosing Open with... > XML Editor. It opened the file and the error didn't occur after that.

Furnivall

Answer 8

I had this problem because a project used IIS and HTTPS, there was no https binding on the IIS, adding a HTTPS binding on the default website fixed the problem.

Allogamy

Answer 9

I was also facing the same issue on the new branch checkout in VS 2019. I just did some changes in web.config and then did undo. it's weird but worked.

Meenen

Answer 10

Well in my case, I did following

1. cleaned solution
2. rebuilt solution
3. Just opened Web.config in the editor

Launch the application and it worked for me.

Project type: ASP.Net MVC Framework: .Net Framework 4.5.2

Solemnity

Interestingly, step 3 solved my problem. I had tried other steps without success. – Leboff

Answer 11

In VSTO, you can't use the designer while debugging another VSTO app.

For example, if another VSTO debugging session is running and you try to invoke the Excel Designer on a different project, you'll get "The Extender Provider failed to return an Extender for this object". Stop debugging to free up the Designer.

Lithesome

Answer 12

For me none of the solutions above worked. I am using VS 2019. In my case, the repository had special characters in the name, so when cloned, the root folder had escaped characters in the name. The compiler could no longer match the file names. Updating the parent folder name and reopening VS fixed the issue.

The detailed error behind 'Extender Provider failed to return an Extender' was related to the inability to find the compiler targets in the path.

Brasserie

Answer 13

In my case I had deleted 'SSL' from the VS2017 C# project properties debug configuration build tab Conditional compilation symbols. Putting it back resolved the error. Apparently SSL require in Debug configuration (but not release).

Matriarch

Answer 14

I had the problem right now, and got help from this thread. It seems its related to web.config being formatted differently from what Visual Studio expects. It might be due to editing web.config on a mac, because when I opened web.config, it detected line breaks that were non-windows, and suggested to replace those. When with CRLF linefeeds. When i said yes to this and saved, the problem went away.

Facile

Answer 15

I am trying to upgrade the .Net framework 4.7.2 to 4.8 and Restarting Visual studio worked for me.

Ludicrous

There must be some detailed information, and proper steps should have mentioned to solve the issue, this make no sense! – Iggy

Answer 16

If you are using visual studio 2017 and the connection string inside the dbml contains "TrustServerCertificate=True;" you will get this error, to resolve it open the dbml file in notepad and remove TrustServerCertificate=True;"

Hamo