During the code cleaning I was doing last week, there was a section that granted a user read only access to a file.
It was nasty code because it involved Active Directory, SIDs, Local Path of UNCs, WMI which was over 100 lines. My cleaned up version only takes 5 lines excluding error handling.
FileInfo fileToAlter = new FileInfo(fullPath);
FileSecurity security = fileToAlter.GetAccessControl();
FileSystemAccessRule rule = new FileSystemAccessRule(userID, FileSystemRights.Read, AccessControlType.Allow);
security.AddAccessRule(rule);
fileToAlter.SetAccessControl(security);
The error handling the code does is to throw an exception with a custom message.
I gained the knowledge from this useful MSDN Article on Managing Access to Windows Objects with ACLs in .Net.
