How to solve this Exception “Culture is not Supported”

Theory

When this issue is not caused by a bug in the application (e.g., duplicate class name):

This issue appears to present after a change is made to the application's project that results in a new build (e.g., code/reference/resource change). The issue appears to lie within the output of this new build: for various reasons Visual Studio is not replacing the entire contents of your application's obj/bin folders. This results in at least some of the contents of your application's bin folder being out of date.

When said issue occurs, clearing out the "Temporary ASP.NET Files" folder, alone, does not solve the problem. It cannot solve the problem, because the stale contents of your application's bin folder are copied back into the "Temporary ASP.NET Files" folder the next time your application is accessed, causing the issue to persist. The key is to remove all existing files and force Visual Studio to rebuild every object, so the next time your application is accessed the new bin files will be copied into the "Temporary ASP.NET Files" folder.

Solution

1. Close Visual Studio
2. Perform an iisreset
3. Delete all the folders and files within the "Temporary ASP.NET Files" folder (the path is referenced in the error message)
4. Delete the offending application's "obj" and "bin" folders
5. Restart Visual Studio and open the solution
6. Perform a "Clean Solution" followed by a "Rebuild Solution"

Explanation

• Steps 1-2: remove resource locks from the folders/files we need to delete.
• Steps 3-4: remove all of the old build files
• Steps 5-6: create new versions of the build files

Looks like you have a query that is taking longer than it should. From your stack trace and your code you should be able to determine exactly what query that is.

This type of timeout can have three causes;

1. There's a deadlock somewhere
2. The database's statistics and/or query plan cache are incorrect
3. The query is too complex and needs to be tuned

A deadlock can be difficult to fix, but it's easy to determine whether that is the case. Connect to your database with Sql Server Management Studio. In the left pane right-click on the server node and select Activity Monitor. Take a look at the running processes. Normally most will be idle or running. When the problem occurs you can identify any blocked process by the process state. If you right-click on the process and select details it'll show you the last query executed by the process.

The second issue will cause the database to use a sub-optimal query plan. It can be resolved by clearing the statistics:

exec sp_updatestats

If that doesn't work you could also try

dbcc freeproccache

You should not do this when your server is under heavy load because it will temporarily incur a big performace hit as all stored procs and queries are recompiled when first executed. However, since you state the issue occurs sometimes, and the stack trace indicates your application is starting up, I think you're running a query that is only run on occasionally. You may be better off by forcing SQL Server not to reuse a previous query plan. See this answer for details on how to do that.

I've already touched on the third issue, but you can easily determine whether the query needs tuning by executing the query manually, for example using Sql Server Management Studio. If the query takes too long to complete, even after resetting the statistics you'll probably need to tune it. For help with that, you should post the exact query in a new question.