file write permission issue under "Program Files" folder

Question

I am using inno setup to make a installation package for my application, and my application is written by C# + .Net 2.0 + VSTS 2008. Inno setup => http://www.jrsoftware.org/isinfo.php and I install my application under Program Files/Foo folder (Foo is my application name). My application is targeting to Windows Vista.

The issue I found is my program cannot write to the folder Program Files/Foo. And I need the permission of write to this folder in order to save some configuration files. The strange thing I notice is the folder Program Files/Foo is marked as readonly and I have checked all folders under Program Files are marked with read only, such as Office.

My questions are,

1. Why all folders are marked as read only under Program Files? It means we should not write to individual application folders under Program Files? If not, where should we write information to disk like user last selected configuration information of an individual application?
2. If we could write to individual application folders under Program Files, what is the solution? I do not want my application to Run As administrator to solve this issue, and if there are solution to write to this folder, I want to require minimal permission if possible.

Answer 1

You should write user specific config data to the Application Data folder for the current user, using the special folders enum and the Enivronment.GetFolderPath.

Answer 2

Best Practice is to not store config data in the Program Files folder. Instead, store your application's data in %AppData%\YourApplicationName. Depending on whether you want to store your config data per-user or in a shared common folder, use one of the following enums to get the folder path:

string userAppData = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);  
string commonAppData = Envrionment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData); 

By default, Vista users do not run programs as Administrators and hence those programs have only read access to the folders under "Program Files". Users can change this behavior by disabling UAC and you could ask your users to do that, but in an office setting users might not have that option. That's why you use AppData instead -- applications can always read and write data to the AppData folder.

Information on UAC can be found at Microsoft's site. Although this page is fairly long, it's a starting point for understanding UAC: http://msdn.microsoft.com/en-us/library/bb530410.aspx