Folder permissions: Full access is granted to all users

Question

I am working on an application that stores some files in a folder CommonApplicationData. My application should modify these files. I was able to create a custom action to grant permissions to fullcontrolmy application folder in the folder CommonApplicationData. But this did not solve the problem for users who are not administrators. When I log in as a user and try to modify one of these files, I get a "Access Denied" message.
How can I solve this problem? Thank.
Here is the code I used in the custom action:

public void GetUsers()
        {
            SelectQuery sQuery = new SelectQuery("Win32_UserAccount", "Domain='" + System.Environment.UserDomainName.ToString() + "'");
            try
            {
                ManagementObjectSearcher mSearcher = new ManagementObjectSearcher(sQuery);
                foreach (ManagementObject mObject in mSearcher.Get())
                {
                    Permission(mObject["Name"].ToString());
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
        private void Permission(string user)
        {
            string directory = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);
            string CompanyFolderPath = Path.Combine(directory, "naseelco\\lms2004");
            DirectoryInfo myDirectoryInfo = new DirectoryInfo(CompanyFolderPath);
            DirectorySecurity myDirectorySecurity = myDirectoryInfo.GetAccessControl();
            string User = System.Environment.UserDomainName + "\\" + user;
            myDirectorySecurity.AddAccessRule(new FileSystemAccessRule(User, FileSystemRights.FullControl, AccessControlType.Allow));
            myDirectoryInfo.SetAccessControl(myDirectorySecurity);
        }

EDIT:
, : . Permission :

private void Permission(string user)
{
  string directory = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);
  string filePath = Path.Combine(directory, "naseelco\\lms2004\\fms.txt");
  FileSecurity fSecurity = File.GetAccessControl(filePath);
  FileSystemAccessRule rule = new FileSystemAccessRule(user, FileSystemRights.FullControl, AccessControlType.Allow);
  fSecurity.SetAccessRule(rule);
  File.SetAccessControl(filePath, fSecurity);
}

Answer 1

Everyone xcacls.exe ACL. .

, . , . Windows , .