Customizing RadGridView Filter Box

        private void radGridView1_ViewCellFormatting(object sender, CellFormattingEventArgs e)
        {
            GridFilterCellElement filterCell = e.CellElement as GridFilterCellElement;
            if (filterCell!=null)
            {
                filterCell.FilterButton.Visibility = ElementVisibility.Collapsed;
            }
        }

        public RadForm1()
        {
            InitializeComponent();
            this.radGridView1.EnableFiltering = true;

            this.radGridView1.ContextMenuOpening+=radGridView1_ContextMenuOpening;
        }

        private void radGridView1_ContextMenuOpening(object sender, ContextMenuOpeningEventArgs e)
        {
            if (e.ContextMenuProvider is GridFilterCellElement)
            {
                foreach (RadItem item in e.ContextMenu.Items)
                {
                    if (item.Text.Contains("Is null")|| item.Text.Contains("Equals"))
                    {
                        item.Visibility = ElementVisibility.Collapsed;
                    }
                }
            }
        }