public void ClosePane( 
   uint id
)

{
  List<uint> myPaneInstanceIDs = [];
  foreach (Pane p in FrameworkApplication.Panes)
  {
    if (p.ContentID == paneID)
    {
      myPaneInstanceIDs.Add(p.InstanceID); //InstanceID of your pane, could be multiple, so build the collection                    
    }
  }
  foreach (var instanceID in myPaneInstanceIDs) //close each of "your" panes.
  {
    FrameworkApplication.Panes.ClosePane(instanceID);
  }
}