public void ClosePane( 
   uint id
)

string _viewPaneID = "my pane"; //DAML ID of your pane
                                //You could have multiple instances (InstanceIDs) of your pane. 
                                //So you can iterate through the Panes to get "your" panes only
IList<uint> myPaneInstanceIDs = new List<uint>();
foreach (Pane pane in FrameworkApplication.Panes)
{
  if (pane.ContentID == _viewPaneID)
  {
    myPaneInstanceIDs.Add(pane.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);
}