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.v23.2.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public DefaultBoolean IsExpandButtonVisible { get; set; }

VB.NET

Public Property IsExpandButtonVisible As DefaultBoolean

Property Value

Type	Description
DefaultBoolean	A DefaultBoolean enumeration value that specifies the expand button’s visibility within the node.

Available values:

Name	Description	Return Value
True	The value is true.	0
False	The value is false.	1
Default	The value is specified by a global option or a higher-level object.	2

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 .

Example

In this example, the TreeListView displays the file/folder tree. The TreeListView.NodeExpanding event allows you to create child nodes dynamically when a user expands a parent node.

View Example: Load Nodes Dynamically

XAML

<dxg:GridControl x:Name="grid">
    <dxg:GridControl.Columns>
        <dxg:GridColumn FieldName="Name"/>
        <dxg:GridColumn FieldName="ItemType"/>
        <dxg:GridColumn FieldName="Size">
            <dxg:GridColumn.EditSettings>
                <dxe:TextEditSettings HorizontalContentAlignment="Right"/>
            </dxg:GridColumn.EditSettings>
        </dxg:GridColumn>
        <dxg:GridColumn FieldName="FullName"/>
    </dxg:GridControl.Columns>
    <dxg:GridControl.View>
        <dxg:TreeListView x:Name="view" 
                          AllowEditing="False"
                          AutoWidth="True"
                          NodeExpanding="OnNodeExpanding"/>
    </dxg:GridControl.View>
</dxg:GridControl>

C#

public partial class MainWindow : Window {
    FileSystemDataProvider Helper { get; set; }
    public MainWindow() {
        InitializeComponent();
        Helper = new FileSystemHelper();
        InitDrives();
    }
    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) };
                view.Nodes.Add(node);
                node.IsExpandButtonVisible = DefaultBoolean.True;
            }
        }
        catch { }
        grid.EndDataUpdate();
    }

    private void OnNodeExpanding(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;
        }
    }

    private void InitFolder(TreeListNode treeListNode) {
        grid.BeginDataUpdate();
        InitFolders(treeListNode);
        InitFiles(treeListNode);
        grid.EndDataUpdate();
    }

    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 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 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;
    }
}

VB.NET

Public Partial Class MainWindow
    Inherits Window

    Private Property Helper As FileSystemDataProvider

    Public Sub New()
        Me.InitializeComponent()
        Helper = New FileSystemHelper()
        InitDrives()
    End Sub

    Public Sub InitDrives()
        Me.grid.BeginDataUpdate()
        Try
            Dim root As String() = Helper.GetLogicalDrives()
            For Each s As String In root
                Dim node As TreeListNode = New TreeListNode() With {.Content = New FileSystemItem(s, "Drive", "<Drive>", s)}
                Me.view.Nodes.Add(node)
                node.IsExpandButtonVisible = DefaultBoolean.True
            Next
        Catch
        End Try

        Me.grid.EndDataUpdate()
    End Sub

    Private Sub OnNodeExpanding(ByVal sender As Object, ByVal e As TreeList.TreeListNodeAllowEventArgs)
        Dim node As TreeListNode = e.Node
        If node.Tag Is Nothing OrElse CBool(node.Tag) = False Then
            InitFolder(node)
            node.Tag = True
        End If
    End Sub

    Private Sub InitFolder(ByVal treeListNode As TreeListNode)
        Me.grid.BeginDataUpdate()
        InitFolders(treeListNode)
        InitFiles(treeListNode)
        Me.grid.EndDataUpdate()
    End Sub

    Private Sub InitFolders(ByVal treeListNode As TreeListNode)
        Dim item As FileSystemItem = TryCast(treeListNode.Content, FileSystemItem)
        If item Is Nothing Then Return
        Try
            Dim root As String() = Helper.GetDirectories(item.FullName)
            For Each s As String In root
                Try
                    Dim node As TreeListNode = New TreeListNode() With {.Content = New FileSystemItem(Helper.GetDirectoryName(s), "Folder", "<Folder>", s)}
                    treeListNode.Nodes.Add(node)
                    node.IsExpandButtonVisible = If(HasFiles(s), DefaultBoolean.True, DefaultBoolean.False)
                Catch
                End Try
            Next
        Catch
        End Try
    End Sub

    Private Sub InitFiles(ByVal treeListNode As TreeListNode)
        Dim item As FileSystemItem = TryCast(treeListNode.Content, FileSystemItem)
        If item Is Nothing Then Return
        Dim node As TreeListNode
        Try
            Dim root As String() = Helper.GetFiles(item.FullName)
            For Each s As String In root
                node = New TreeListNode() With {.Content = New FileSystemItem(Helper.GetFileName(s), "File", Helper.GetFileSize(s).ToString(), s)}
                node.IsExpandButtonVisible = DefaultBoolean.False
                treeListNode.Nodes.Add(node)
            Next
        Catch
        End Try
    End Sub

    Private Function HasFiles(ByVal path As String) As Boolean
        Dim root As String() = Helper.GetFiles(path)
        If root.Length > 0 Then Return True
        root = Helper.GetDirectories(path)
        If root.Length > 0 Then Return True
        Return False
    End Function
End Class

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the IsExpandButtonVisible property.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

wpf-treelist-load-nodes-dynamically/CS/DynamicNodeLoading/MainWindow.xaml.cs#L21

    view.Nodes.Add(node);
    node.IsExpandButtonVisible = DefaultBoolean.True;
}

VB.NET

wpf-treelist-load-nodes-dynamically/VB/DynamicNodeLoading/MainWindow.xaml.vb#L25

    Me.view.Nodes.Add(node)
    node.IsExpandButtonVisible = DefaultBoolean.True
Next