TreeListNode.IsExpandButtonVisible Property

Gets or sets whether the expand button is displayed within the node or not.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v20.1.dll

Declaration

public DefaultBoolean IsExpandButtonVisible { get; set; }
Public Property IsExpandButtonVisible As DefaultBoolean

Property Value

Type Description
DefaultBoolean

A DefaultBoolean enumeration value that specifies the expand button's visibility within the node.

Remarks

The TreeListView.NodeExpanding event can be handled to dynamically create child nodes. In this instance, when expanding a node, you do not know whether it has child nodes or not. If the node has no child nodes, hide the expand button by setting the IsExpandButtonVisible property to false.

To learn more, see Expanding and Collapsing Nodes .

Examples

In this example, the TreeListView displays the file/folder tree. Child nodes that correspond to sub folders or files contained within a folder are dynamically created when a parent node is being expanded.

using System;
using System.Windows;
using DevExpress.Xpf.Grid;
using System.IO;
using DevExpress.Utils;

namespace DynamicNodeLoading {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
            Helper = new FileSystemHelper();
            InitDrives();
        }

        private void treeListView1_NodeExpanding(object sender, DevExpress.Xpf.Grid.TreeList.TreeListNodeAllowEventArgs e) {
            TreeListNode node = e.Node;
            if (node.Tag == null || (bool)node.Tag == false) {
                InitFolder(node);
                node.Tag = true;
            }
        }

        FileSystemDataProvider Helper { get; set; }

        public void InitDrives() {
            grid.BeginDataUpdate();
            try {
                string[] root = Helper.GetLogicalDrives();

                foreach (string s in root) {
                    TreeListNode node = new TreeListNode() { Content = new FileSystemItem(s, "Drive", "<Drive>", s) };
                    treeListView1.Nodes.Add(node);
                    node.IsExpandButtonVisible = DefaultBoolean.True;
                }
            }
            catch { }
            grid.EndDataUpdate();
        }
        private void InitFolder(TreeListNode treeListNode) {
            grid.BeginDataUpdate();
            InitFolders(treeListNode);
            InitFiles(treeListNode);
            grid.EndDataUpdate();
        }

        private void InitFiles(TreeListNode treeListNode) {
            FileSystemItem item = treeListNode.Content as FileSystemItem;
            if (item == null) return;
            TreeListNode node;
            try {
                string[] root = Helper.GetFiles(item.FullName);
                foreach (string s in root) {
                    node = new TreeListNode() { Content = new FileSystemItem(Helper.GetFileName(s), "File", Helper.GetFileSize(s).ToString(), s) };
                    node.IsExpandButtonVisible = DefaultBoolean.False;
                    treeListNode.Nodes.Add(node);
                }
            }
            catch { }
        }

        private void InitFolders(TreeListNode treeListNode) {
            FileSystemItem item = treeListNode.Content as FileSystemItem;
            if (item == null) return;

            try {
                string[] root = Helper.GetDirectories(item.FullName);
                foreach (string s in root) {
                    try {
                        TreeListNode node = new TreeListNode() { Content = new FileSystemItem(Helper.GetDirectoryName(s), "Folder", "<Folder>", s) };
                        treeListNode.Nodes.Add(node);

                        node.IsExpandButtonVisible = HasFiles(s) ? DefaultBoolean.True : DefaultBoolean.False;
                    }
                    catch { }
                }
            }
            catch { }
        }

        private bool HasFiles(string path) {
            string[] root = Helper.GetFiles(path);
            if (root.Length > 0) return true;
            root = Helper.GetDirectories(path);
            if (root.Length > 0) return true;
            return false;
        }
        public abstract class FileSystemDataProvider {
            public abstract string[] GetLogicalDrives();
            public abstract string[] GetDirectories(string path);
            public abstract string[] GetFiles(string path);
            public abstract string GetDirectoryName(string path);
            public abstract string GetFileName(string path);
            public abstract long GetFileSize(string path);
        }
        public class FileSystemHelper : FileSystemDataProvider {

            public override string[] GetLogicalDrives() {
                return Directory.GetLogicalDrives();
            }

            public override string[] GetDirectories(string path) {
                return Directory.GetDirectories(path);
            }

            public override string[] GetFiles(string path) {
                return Directory.GetFiles(path);
            }

            public override string GetDirectoryName(string path) {
                return new DirectoryInfo(path).Name;
            }

            public override string GetFileName(string path) {
                return new FileInfo(path).Name;
            }

            public override long GetFileSize(string path) {
                return new FileInfo(path).Length;
            }
        }
    }

    public class FileSystemItem {
        public FileSystemItem(string name, string type, string size, string fullName) {
            Name = name;
            ItemType = type;
            Size = size;
            FullName = fullName;
        }
        public string Name { get; set; }
        public string ItemType { get; set; }
        public string Size { get; set; }
        public string FullName { get; set; }
    }
}
See Also