How do I give ASP.NET permission to write to a folder in Windows 7?

Giving write permissions to all IIS_USRS group is a bad idea from the security point of view. You dont need to do that and you can go with giving permissions only to system user running the application pool.

If you are using II7 (and I guess you do) do the following.

1. Open IIS7
2. Select Website for which you need to modify permissions
3. Go to Basic Settings and see which application pool you're using.
4. Go to Application pools and find application pool from #3
5. Find system account used for running this application pool (Identity column)
6. Navigate to your storage folder in IIS, select it and click on Edit Permissions (under Actions sub menu on the right)
7. Open security tab and add needed permissions only for user you identified in #3

Note #1: if you see ApplicationPoolIdentity in #3 you need to reference this system user like this IIS AppPool{application_pool_name} . For example IIS AppPool\DefaultAppPool

Note #2: when adding this user make sure to set correct locations in the Select Users or Groups dialog. This needs to be set to local machine because this is local account.

I know this is an old thread but to further expand the answer here, by default IIS 7.5 creates application pool identity accounts to run the worker process under. You can't search for these accounts like normal user accounts when adding file permissions. To add them into NTFS permission ACL you can type the entire name of the application pool identity and it will work.

It is just a slight difference in the way the application pool identity accounts are handle as they are seen to be virtual accounts.

Also the username of the application pool identity is "IIS AppPool\application pool name" so if it was the application pool DefaultAppPool the user account would be "IIS AppPool\DefaultAppPool".

These can be seen if you open computer management and look at the members of the local group IIS_IUSRS. The SID appended to the end of them is not need when adding the account into an NTFS permission ACL.

Hope that helps

My immediate solution (since I couldn't find the ASP.NET worker process) was to give write (that is, Modify) permission to IIS_IUSRS. This worked. I seem to recall that in WinXP I had to specifically given the ASP.NET worker process write permission to accomplish this. Maybe my memory is faulty, but anyway...

@DraganRadivojevic wrote that he thought this was dangerous from a security viewpoint. I do not disagree, but since this was my workstation and not a network server, it seemed relatively safe. In any case, his answer is better and is what I finally settled on after chasing down a fail-path due to not specifying the correct domain for the AppPool user.