“CS0016: Could not write to output file” error when starting an app in IIS 7

Question

I am running Windows 7, and am not usually a developer in this setting, and have recently built a WCF Rest Service in C#, that I\'m now trying to deploy to IIS just on my lo

Answer 1

I was getting the same error while developing a web api using asp.net core 2.0 and it got resolved after restarting the machine.

Answer 2

I started getting this error too recently in a corporate environment after the company implemented various security measures that took away admin rights from the users.

For developers, the company authorized the creation of accounts that could be used and we had to add these to the PC's admin group and then change the application pool's identity to use the account.

EXAMPLE (Windows 10)

Account created for developers: domain\developer

Someone with admin rights to the PC will have to do the following:

• Go to Control Panel\User Accounts\Manage User Accounts
• Click on the Advanced tab, and click on the Advanced user management button
• In the lusrmgr page, click on the Groups folder in the left column to bring up groups in the center panel
• Then secondary-click on the Administrators group and select "Add to Group..."
• In the Administrators Properties panel, click the "Add..." button
• A "Select Users, Computers, Service Accounts, or Groups" dialog opens. Add the account (domain\developer in this example)
• Then click on the OK button (this button will be disabled if you don't have admin rights)

Now configure the App Pool:

• Open IIS Manager, select Application Pools
• Click on the application pool you want so it's highlighted, then click "Advanced Settings..." from the Actions panel on the right
• Under the Process Model section, click on the Identity setting and the ellipses button
• In the Application Pool Identity dialog, select "Custom account" and then click the Set button
• Enter the account and the password

At this point I was able to close everything, restart IIS and then run my app. It could then access the temp folders it couldn't before.

Answer 3

For those looking here as I did, if the accepted answer doesn't resolve the issue you might try following this article: http://lordzoltan.blogspot.com/2011/02/aspnet-2-and-4-default-application-pool.html

In summary, it seems that the same error is sometimes displayed when the app pool user doesn't have access to the %TMP%/%TEMP% folder.

You'll need to grant IIS_IUSRS read and modify access over the temp folder of the user the app pool is running as.

This could either be the temp folder in the app pool user's profile, e.g. c:\Windows\ServiceProfiles\NetworkService\AppData\Local\Temp, or the system temp folder at c:\windows\temp.

Setting this up this resolved the issue for me.

Answer 4

I granted read and write access to C:\Windows\Temp for the IIS_WPG group. This worked for me. I'm on Server 2003 R2 and IIS 6 and the group name is different. I fount it from http://learn.iis.net/page.aspx/140/understanding-built-in-user-and-group-accounts-in-iis/ where it says:

•The IUSR built-in account replaces the IUSR_MachineName account.

•The IIS_IUSRS built-in group replaces the IIS_WPG group.

Thanks to Dommer for suggesting the windows temp folder and to zcrar70 for the nice summery and a link with detailed description.

Answer 5

On Windows 8 absolutely nothing worked for me. One day app pools suddenly decided they no longer want to work under the NetworkService account.

I solved the problem by changing the app pool to work under my own user account. Not a great solution I know, but it worked.

Answer 6

Some times the Temp files might be locked by other process in the workstation. As a first step please reboot the workstation and check the application.