Changing permissions on child folders in C#

Question

I'm writing a DLL to change permissions on a folder and everything underneath the folder. Below is the code that I have right now.

The problem comes when I call addPermissions(). It's correctly setting the permissions on the dirName folder and any folder that I later create under dirName, but any folder that exists when I add permissions doesn't get the additional permissions.

Do I need to recursively set the permissions on all child folders? Or is there a way to do this with a line or two of code?

public class Permissions
{
    public void addPermissions(string dirName, string username)
    {
        changePermissions(dirName, username, AccessControlType.Allow);
    }

    public void revokePermissions(string dirName, string username)
    {
        changePermissions(dirName, username, AccessControlType.Deny);
    }

    private void changePermissions(string dirName, string username, AccessControlType newPermission)
    {
        DirectoryInfo myDirectoryInfo = new DirectoryInfo(dirName);

        DirectorySecurity myDirectorySecurity = myDirectoryInfo.GetAccessControl();

        string user = System.Environment.UserDomainName + "\\" + username;

        myDirectorySecurity.AddAccessRule(new FileSystemAccessRule(
            user, 
            FileSystemRights.Read | FileSystemRights.Write | FileSystemRights.ExecuteFile | FileSystemRights.Delete, 
            InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit, 
            PropagationFlags.InheritOnly, 
            newPermission
        ));

        myDirectoryInfo.SetAccessControl(myDirectorySecurity);
    }
}

Answer 1

You have to do it recursively. You can specify inheritance rules for new folders/files but for existing you have to do it yourself.