Copy the data from XML file and paste in same file and overwrite using file.copy()

I am trying to copy data of one file and pasting it into the same file which means overwriting it. I learn that overwrite the file data using file.copy() cannot be possible. but from the one of the post says that if I use File.Copy(Source file, destination file, true) than overwrite is possible. I tried to use but it didn't work. if anyone have solution for that than it will be big help.

  public void EditRole(string oldRole, string newRole)
        {
          if (File.Exists(roleXMLLoc))
            {
                XDocument doc = XDocument.Load(roleXMLLoc);
                var edit = doc.Element("Roles").Elements("Role").Where(x => x.Value == oldRole).SingleOrDefault();
                edit.Value = newRole;
                doc.Save(roleXMLLoc);

                if (File.Exists(userPermissionLoc))
                {
                  File.Copy(userPermissionLoc, userPermissionLoc, true); SaveData();
                }
          }
}