Custom GridView Filter Popup

        public RadForm1()
        {
            InitializeComponent();

            this.radGridView1.Columns.Add("Name");
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;

            this.radGridView1.Rows.Add("A");
            this.radGridView1.Rows.Add("B");
            this.radGridView1.Rows.Add("C");
            this.radGridView1.Rows.Add("D");

            this.radGridView1.EnableFiltering = true;
            this.radGridView1.ShowHeaderCellButtons = true;
            this.radGridView1.ShowFilteringRow = false;

            this.radGridView1.FilterPopupInitialized+=radGridView1_FilterPopupInitialized;
        }

        private void radGridView1_FilterPopupInitialized(object sender, FilterPopupInitializedEventArgs e)
        {
            RadListFilterPopup popup = e.FilterPopup as RadListFilterPopup;
            if (popup != null)
            {
                popup.MenuElement.Items.RemoveAt(0);
                popup.MenuElement.Items.RemoveAt(0);

                popup.MenuTreeElement.DistinctListValues.Add("<empty>", "");
                popup.MenuTreeElement.DistinctListValues.Remove("C");
                popup.MenuTreeElement.DistinctListValues.Remove("D");
            }
        }