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Server Error in Application An unhandled exception occurred during the execution of the current web request

Mutex Could not be Created.

Some time while running ASP.NET web application through Visual Studio you might receive following error

Server Error in Application. Mutex could not be created.

Few workaround for “Mutex Could not be Created.”

“Mutex Could not be Created.”

Solution number 1
1. If your visual studio 2005 is open, closed it.
2. Go to the ASP.NET temporary folder for v2.0 of the framework
\Microsoft.Net\Framework\v2.0\Temporary ASpNET pages 3. Remove the folder for your application
4. Reset IIS (iisreset)
5. First Browse your page from Browser
6. Re-open Visual studio

“Mutex Could not be Created.”

Solution number 2
1. locate the current machine config file (e.g at C:\WINNT\Microsoft.NET\Framework\v2.0.50727\CONFIG\)
2. update the Machine.Config under the tag like that -

“Mutex Could not be Created.”

Solution number 3
Cause: This occurs because the permissions on the following registry key no longer have your custom account:
The compilation mutex gets it's permissions from this registry key and with your custom account missing, the process running ASP.NET cannot get a handle to the mutex and fails during compilation.
1. Run the following to add your custom account to the registry key permissions:
ASPNET_regiis -ga domain\account.
2. Either restart the server or close the handles to the mutex (see below)
To close the handles to the Mutex:
3. Download and launch Process Explorer from
4. From the Find menu, select Find Handle or DLL
5. In the Handle or DLL substring box, type “mutant” (without quotes) and click Search
6. Click the Handle or DLL column heading to sort the items and find a mutex that starts with CL. The handle will typically be devenv.exe (the IDE for Visual Studio) and aspnet_wp.exe or w3wp.exe. The handle will look similar to:
7. \BaseNameObjects\CLbdd6aa8f
8. Select the handle in the search box and Process Explorer locates the Process and the handle in the main window
9. Right-click the handle in the main window and select Close Handle
Additional Info:
The error may occur anytime you run ASP.NET as a custom account and the above mentioned registry key does not have the account listed in the permissions.
If you receive the error and you are running with a custom account on IIS 6 in worker process mode (code running in w3wp.exe), you can add your custom account to the IIS_WPG group on the server. The IIS_WPG group is granted access to the registry key by default.

“Mutex Could not be Created.”

Solution Number 4
You may also need to fix the perimssions manually, as follows:
1. Run Registry Editor 32: Windows -> Run -> "REGEDT32"
2. Locate the sub-window "HKEY_LOCAL_MACHINE on Local Machine"
3. Navigate to the key:
(and select it).
4. Click the menu "Security" then "Permissions".
5. Ensure the custom account you are using to run aspnet (e.g. "mydomain\aspnet") is in this permissions list.
If it is not then Add it and ensure "Full Control" is ticked, then click OK.
6. This should immediately resolve the Mutex locking issue (just refresh your page, or rebuild in Visual Studio).
7. If not then do an IISRESET first then retry step 6.

“Mutex Could not be Created.”

Solution number 5
Go to the Visual Studio Command Prompt and reach at
and type the command
c:\Windows\\Framework\v2.0.50727> aspnet_regiis -ga Domain\User
After that, go to the windows\\framework\v2.0.50727 and there you'll get a temporary file. Just delete it without any hasitation. Rfresh and restart the IIS.

“Mutex Could not be Created.”

Solution number 6 On Vista Business 1. Delete my app from the aspnet folder
2. Opened Regedit. Went to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ASP.NET\2.050727.0. Right clicked and added aspnet as user providing it full-control permissions.
Hope this help!!!....

Posted on Thursday, December 27, 2007 6:28 AM unhandled exception | Back to top

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