/// <summary>
        /// Handles when a filter is removed from the collection.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="MapDrawFilterHelperCollectionEventArgs"/> instance containing the event data.</param>
        void _filterCollection_Removed(MapDrawFilterHelperCollection sender, MapDrawFilterHelperCollectionEventArgs e)
        {
            // Remove the filter from the ToolBarControl's DropDownItems

            FilterToolStripItem ftsi;

            if (!_tsFilters.TryGetValue(e.Filter, out ftsi))
            {
                const string errmsg = "Failed to find FilterToolStripItem for filter `{0}`.";
                if (log.IsErrorEnabled)
                {
                    log.ErrorFormat(errmsg, e.Filter);
                }
                Debug.Fail(string.Format(errmsg, e.Filter));
                return;
            }

            Debug.Assert(ftsi.Filter == e.Filter);

            _tsFilters.Remove(e.Filter);
            ftsi.Dispose();

            // If the filter we just got rid of was the active one, set the active filter to null
            if (e.Filter == _currentFilter)
            {
                _currentFilter = null;
            }
        }
        /// <summary>
        /// Handles hwen a filter is added to the collection.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="MapDrawFilterHelperCollectionEventArgs"/> instance containing the event data.</param>
        void _filterCollection_Added(MapDrawFilterHelperCollection sender, MapDrawFilterHelperCollectionEventArgs e)
        {
            // Add the new filter to the ToolBarControl's DropDownItems

            var ftsi = new FilterToolStripItem(e.Filter, e.FilterName);

            ftsi.CheckedChanged += ftsi_CheckedChanged;

            _tsFilters.Add(e.Filter, ftsi);

            var s = ToolBarControl.ControlSettings.AsSplitButtonSettings();

            s.DropDownItems.Insert(0, ftsi);
        }
        /// <summary>
        /// Handles when a filter is removed from the collection.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="MapDrawFilterHelperCollectionEventArgs"/> instance containing the event data.</param>
        void _filterCollection_Removed(MapDrawFilterHelperCollection sender, MapDrawFilterHelperCollectionEventArgs e)
        {
            // Remove the filter from the ToolBarControl's DropDownItems

            FilterToolStripItem ftsi;
            if (!_tsFilters.TryGetValue(e.Filter, out ftsi))
            {
                const string errmsg = "Failed to find FilterToolStripItem for filter `{0}`.";
                if (log.IsErrorEnabled)
                    log.ErrorFormat(errmsg, e.Filter);
                Debug.Fail(string.Format(errmsg, e.Filter));
                return;
            }

            Debug.Assert(ftsi.Filter == e.Filter);

            _tsFilters.Remove(e.Filter);
            ftsi.Dispose();

            // If the filter we just got rid of was the active one, set the active filter to null
            if (e.Filter == _currentFilter)
                _currentFilter = null;
        }
        /// <summary>
        /// Handles hwen a filter is added to the collection.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="MapDrawFilterHelperCollectionEventArgs"/> instance containing the event data.</param>
        void _filterCollection_Added(MapDrawFilterHelperCollection sender, MapDrawFilterHelperCollectionEventArgs e)
        {
            // Add the new filter to the ToolBarControl's DropDownItems

            var ftsi = new FilterToolStripItem(e.Filter, e.FilterName);
            ftsi.CheckedChanged += ftsi_CheckedChanged;

            _tsFilters.Add(e.Filter, ftsi);

            var s = ToolBarControl.ControlSettings.AsSplitButtonSettings();
            s.DropDownItems.Insert(0, ftsi);
        }