右键弹出菜单 并动态新增菜单子项

private void vAssetDetailDataGridView_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
        {
            if (e.Button == MouseButtons.Right)
            {
                if (e.RowIndex >= 0)
                {
                    if (vAssetDetailDataGridView.Rows[e.RowIndex].Selected == false)
                    {
                        vAssetDetailDataGridView.ClearSelection();
                        vAssetDetailDataGridView.Rows[e.RowIndex].Selected = true;
                    }
                    string typename = vAssetDetailDataGridView.Rows[e.RowIndex].Cells[0].Value.ToString();
                    AssetType listtype = AssetTypeBLL.QueryAllAssetType().FirstOrDefault<AssetType>(p => p.TypeName == typename) as AssetType;

                    if (listtype != null)
                    {
                        List<AssetTypeExtend> listextend = AssetTypeBLL.QueryAssetTypeExtend(listtype.Id);
                        cmsTypeExtend.Items.Clear();
                        for (int i = 0; i < listextend.Count; i++)
                        {
                            cmsTypeExtend.Items.Add(listextend[i].ExtendName);
                        }
                    }
                    else
                    {
                        cmsTypeExtend.Text = "暂无属性";
                    }                    
                    
                    cmsTypeExtend.Show(MousePosition.X, MousePosition.Y);
                }
            }
        }