Winform使用DataGridView实现下拉筛选

/// <summary>
        /// 显示筛选面板
        /// </summary>
        public new void Show()
        {
            if (GridView == null) { return; }
            //获取点击的列
            Point point = GridView.PointToClient(Cursor.Position);
            DataGridView.HitTestInfo hit = GridView.HitTest(point.X, point.Y);
            if (hit.ColumnIndex > -1)
            {
                //加入到筛选面板中
                list_filter.Items.Clear();
                List<string> items = new List<string>();
                foreach (DataGridViewRow row in GridView.Rows)
                {
                    string value =Convert.ToString(row.Cells[hit.ColumnIndex].Value);
                    if (!items.Contains(value))
                    {
                        items.Add(value);
                    }
                }
                list_filter.Items.AddRange(items.ToArray());
                //定位筛选面板的位置
                Location = new Point(hit.ColumnX, hit.RowY);
                Visible = true;
            }
        }
        /// <summary>
        /// 隐藏筛选面板
        /// </summary>
        public new void Hide()
        {
            if (Visible)
            {
                Visible = false;
            }
        }
        /// <summary>
        /// 点击筛选事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void list_filter_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (list_filter.SelectedIndex > -1)
            {
                string selectValue = list_filter.Items[list_filter.SelectedIndex].ToString();
                //获取点击的列
                Point point = GridView.PointToClient(Cursor.Position);
                DataGridView.HitTestInfo hit = GridView.HitTest(point.X, point.Y);
                if (hit.ColumnIndex > -1)
                {
                    for (int i = 0; i < GridView.Rows.Count; i++)
                    {
                        string value = Convert.ToString(GridView.Rows[i].Cells[hit.ColumnIndex].Value);
                        if (GridView.Rows[i].IsNewRow) continue;
                        if (selectValue != value)
                        {
                            //存储被筛选掉的数据
                            FilterData[hit.ColumnIndex].Add(DeepCopy(GridView.Rows[i]));
                            //清除被筛选掉的数据
                            GridView.Rows.RemoveAt(i);
                            i--;
                        }
                    }
                }
                //筛选完后隐藏
                Hide();
            }
        }

protected override void OnCellPainting(DataGridViewCellPaintingEventArgs e)
        {
            base.OnCellPainting(e);
            if (e.RowIndex == -1 && e.ColumnIndex > -1)
            {
                //绘制筛选图标
                Rectangle rect = new Rectangle(e.CellBounds.Right - 10, 5, 5, 5);
                e.Paint(rect, DataGridViewPaintParts.All);
                e.Graphics.DrawString("◊", new Font("宋体", 5), Brushes.Black, rect.X, rect.Y);
                e.Handled = true;
            }
        }
        protected override void OnCellMouseClick(DataGridViewCellMouseEventArgs e)
        {
            base.OnCellMouseClick(e);
            if (e.Button == MouseButtons.Left)
            {
                HitTestInfo hit = HitTest(e.X, e.Y);
                if (hit.Type == DataGridViewHitTestType.ColumnHeader)
                {
                    Rectangle headerCellRect = GetColumnDisplayRectangle(hit.ColumnIndex, false);
                    if (e.X > headerCellRect.Width - 20)
                    {
                        filterPanel.Show();
                        return;
                    }
                }
            }
            filterPanel.Hide();
        }

DataTable dt = new DataTable();
dt.Columns.Add("ID");
            dt.Columns.Add("Name");
            for (int i = 0; i < 10; i++)
            {
                dt.Rows.Add(i, "name" + i);
            }
            for (int i = 0; i < 10; i++)
            {
                dt.Rows.Add(i, "name" + i + "_1");
            }
            gridViewFilter1.DataSource = dt;