public RadForm1()
        {
            InitializeComponent();            

           this.radCommandBar1.ToolTipTextNeeded+=radCommandBar1_ToolTipTextNeeded;
        } 

        private void radCommandBar1_ToolTipTextNeeded(object sender, ToolTipTextNeededEventArgs e)
        {
            e.ToolTip.OwnerDraw = true;

            e.ToolTip.Popup -= ToolTip_Popup;
            e.ToolTip.Popup += ToolTip_Popup;

            e.ToolTip.Draw -= ToolTip_Draw;
            e.ToolTip.Draw += ToolTip_Draw;
        }
        void ToolTip_Popup(object sender, PopupEventArgs e)
        {
            e.ToolTipSize = TextRenderer.MeasureText(this.commandBarButton1.ToolTipText, new Font("Arial", 16.0f));
            Console.WriteLine(e.ToolTipSize);
        }

        void ToolTip_Draw(object sender, DrawToolTipEventArgs e)
        {
            using (e.Graphics)
            {
                Font f = new Font("Arial", 16.0f);
                e.DrawBackground();
                e.DrawBorder();
                this.commandBarButton1.ToolTipText = e.ToolTipText;
                e.Graphics.DrawString(e.ToolTipText, f, Brushes.Black, new Point(2, 2));

            }
        }