internal ResortCallback(
                UpdateColumnSortCommand owner,
                SortDescriptionCollection sortDescriptions,
                ColumnCollection columns)
            {
                if (owner == null)
                {
                    throw new ArgumentNullException("owner");
                }

                m_owner            = new WeakReference(owner);
                m_sortDescriptions = sortDescriptions;
                m_columns          = columns;
            }
      internal ResortCallback(
        UpdateColumnSortCommand owner,
        SortDescriptionCollection sortDescriptions,
        ColumnCollection columns )
      {
        if( owner == null )
          throw new ArgumentNullException( "owner" );

        m_owner = new WeakReference( owner );
        m_sortDescriptions = sortDescriptions;
        m_columns = columns;
      }