Form1.cs

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using DevExpress.XtraNavBar;

namespace ExpandingGroup
{
	/// <summary>
	/// Summary description for Form1.
	/// </summary>
    public class Form1 : System.Windows.Forms.Form {
        private DevExpress.XtraNavBar.NavBarControl navBarControl1;
        private DevExpress.XtraNavBar.NavBarGroup navBarGroup1;
        private DevExpress.XtraNavBar.NavBarGroup navBarGroup2;
        private DevExpress.XtraNavBar.NavBarItem navBarItem1;
        private DevExpress.XtraNavBar.NavBarItem navBarItem2;
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;

        public Form1() {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();

            //
            // TODO: Add any constructor code after InitializeComponent call
            //
        }

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing ) {
            if( disposing ) {
                if (components != null) {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent() {
            this.navBarControl1 = new DevExpress.XtraNavBar.NavBarControl();
            this.navBarGroup1 = new DevExpress.XtraNavBar.NavBarGroup();
            this.navBarItem1 = new DevExpress.XtraNavBar.NavBarItem();
            this.navBarGroup2 = new DevExpress.XtraNavBar.NavBarGroup();
            this.navBarItem2 = new DevExpress.XtraNavBar.NavBarItem();
            ((System.ComponentModel.ISupportInitialize)(this.navBarControl1)).BeginInit();
            this.SuspendLayout();
            // 
            // navBarControl1
            // 
            this.navBarControl1.ActiveGroup = this.navBarGroup1;
            this.navBarControl1.Groups.AddRange(new DevExpress.XtraNavBar.NavBarGroup[] {
            this.navBarGroup1,
            this.navBarGroup2});
            this.navBarControl1.Items.AddRange(new DevExpress.XtraNavBar.NavBarItem[] {
            this.navBarItem1,
            this.navBarItem2});
            this.navBarControl1.Location = new System.Drawing.Point(16, 8);
            this.navBarControl1.Name = "navBarControl1";
            this.navBarControl1.OptionsNavPane.ExpandedWidth = 168;
            this.navBarControl1.Size = new System.Drawing.Size(168, 300);
            this.navBarControl1.TabIndex = 0;
            this.navBarControl1.Text = "navBarControl1";
            this.navBarControl1.MouseUp += new System.Windows.Forms.MouseEventHandler(this.navBarControl1_MouseUp);
            // 
            // navBarGroup1
            // 
            this.navBarGroup1.Caption = "navBarGroup1";
            this.navBarGroup1.ItemLinks.AddRange(new DevExpress.XtraNavBar.NavBarItemLink[] {
            new DevExpress.XtraNavBar.NavBarItemLink(this.navBarItem1)});
            this.navBarGroup1.Name = "navBarGroup1";
            // 
            // navBarItem1
            // 
            this.navBarItem1.Caption = "navBarItem1";
            this.navBarItem1.Name = "navBarItem1";
            // 
            // navBarGroup2
            // 
            this.navBarGroup2.Caption = "navBarGroup2";
            this.navBarGroup2.ItemLinks.AddRange(new DevExpress.XtraNavBar.NavBarItemLink[] {
            new DevExpress.XtraNavBar.NavBarItemLink(this.navBarItem2)});
            this.navBarGroup2.Name = "navBarGroup2";
            // 
            // navBarItem2
            // 
            this.navBarItem2.Caption = "navBarItem2";
            this.navBarItem2.Name = "navBarItem2";
            // 
            // Form1
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(312, 322);
            this.Controls.Add(this.navBarControl1);
            this.Name = "Form1";
            this.Text = "Which event to use when collapsing/expanding the groups in the NavBar\'s Explorer " +
                "views?";
            ((System.ComponentModel.ISupportInitialize)(this.navBarControl1)).EndInit();
            this.ResumeLayout(false);

        }
        #endregion

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main() {
            Application.Run(new Form1());
        }

        private void navBarControl1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e) {
            if(e.Button == MouseButtons.Left) {
                NavBarHitInfo info = (sender as NavBarControl).CalcHitInfo(new Point(e.X, e.Y));
                if(info.InGroupButton && !info.Group.Expanded) {
                    if(MessageBox.Show("Expand group?", "Confirmation", MessageBoxButtons.YesNo) == DialogResult.Yes)
                        info.Group.Expanded = true;
                    else
                        ((DevExpress.Utils.DXMouseEventArgs)e).Handled = true;
                }
            }
        }
    }
}