Iterate Through Nodes

• Apr 04, 2019
• 7 minutes to read

The Node Iterator allows you to traverse through the nodes without writing recursive code. Nodes are visited one by one starting from a specified node down to the last node contained within a tree.

The image below illustrates the sequence in which nodes are processed.

To iterate through the nodes, do the following.

• Create a new instance of the TreeListNodeIterator class. Multiple constructors allow you to specify a start node or a collection of nodes, along with whether to process only visible nodes.

  Note

  If you have specified a collection of nodes, nodes are processed starting from the first node within a specified collection.

• Use the TreeListNodeIterator.MoveNext method to iterate through nodes. The currently processed node is returned by the TreeListNodeIterator.Current property. Each time the TreeListNodeIterator.MoveNext method is called, the Node Iterator moves to the next node in the hierarchy and updates the TreeListNodeIterator.Current property. If the current node is the last node, the TreeListNodeIterator.MoveNext method returns false.

  To reset the Node Iterator to its initial state, call the TreeListNodeIterator.Reset method.

Example: How to Iterate Through All Visible Nodes

This example shows how to traverse through all visible nodes to expand those nodes that have more than four child nodes. Nodes that have less than four child nodes are collapsed.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-iterate-through-nodes-via-the-node-iterator-e3102.

MainWindow.xaml

<Window xmlns:dxg="clr-namespace:DevExpress.Xpf.Grid;assembly=DevExpress.Xpf.Grid.v11.1"  x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
        dx:ThemeManager.ThemeName="Office2007Black"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <dxg:GridControl Name="grid" Loaded="grid_Loaded">
            <dxg:GridControl.Columns>
                <dxg:GridColumn FieldName="Name"/>
                <dxg:GridColumn FieldName="Department"/>
                <dxg:GridColumn FieldName="Position"/>
            </dxg:GridControl.Columns>
            <dxg:GridControl.View>
                <dxg:TreeListView Name="treeListView" AutoWidth="True"
                                  KeyFieldName="ID" ParentFieldName="ParentID"/>
            </dxg:GridControl.View>
        </dxg:GridControl>
    </Grid>
</Window>

Employees.cs

using System;
using System.Collections.Generic;

public class Employee {
    public int ID { get; set; }
    public int ParentID { get; set; }
    public string Name { get; set; }
    public string Position { get; set; }
    public string Department { get; set; }
}

public static class Stuff {
    public static List<Employee> GetStuff() {
        List<Employee> stuff = new List<Employee>();
        stuff.Add(new Employee() { ID = 1, ParentID = 0, Name = "Gregory S. Price", Department = "", Position = "President" });
        stuff.Add(new Employee() { ID = 2, ParentID = 1, Name = "Irma R. Marshall", Department = "Marketing", Position = "Vice President" });
        stuff.Add(new Employee() { ID = 3, ParentID = 1, Name = "John C. Powell", Department = "Operations", Position = "Vice President" });
        stuff.Add(new Employee() { ID = 4, ParentID = 1, Name = "Christian P. Laclair", Department = "Production", Position = "Vice President" });
        stuff.Add(new Employee() { ID = 5, ParentID = 1, Name = "Karen J. Kelly", Department = "Finance", Position = "Vice President" });

        stuff.Add(new Employee() { ID = 6, ParentID = 2, Name = "Brian C. Cowling", Department = "Marketing", Position = "Manager" });
        stuff.Add(new Employee() { ID = 7, ParentID = 2, Name = "Thomas C. Dawson", Department = "Marketing", Position = "Manager" });
        stuff.Add(new Employee() { ID = 8, ParentID = 2, Name = "Angel M. Wilson", Department = "Marketing", Position = "Manager" });
        stuff.Add(new Employee() { ID = 9, ParentID = 2, Name = "Bryan R. Henderson", Department = "Marketing", Position = "Manager" });

        stuff.Add(new Employee() { ID = 10, ParentID = 3, Name = "Harold S. Brandes", Department = "Operations", Position = "Manager" });
        stuff.Add(new Employee() { ID = 11, ParentID = 3, Name = "Michael S. Blevins", Department = "Operations", Position = "Manager" });
        stuff.Add(new Employee() { ID = 12, ParentID = 3, Name = "Jan K. Sisk", Department = "Operations", Position = "Manager" });
        stuff.Add(new Employee() { ID = 13, ParentID = 3, Name = "Sidney L. Holder", Department = "Operations", Position = "Manager" });

        stuff.Add(new Employee() { ID = 14, ParentID = 4, Name = "James L. Kelsey", Department = "Production", Position = "Manager" });
        stuff.Add(new Employee() { ID = 15, ParentID = 4, Name = "Howard M. Carpenter", Department = "Production", Position = "Manager" });
        stuff.Add(new Employee() { ID = 16, ParentID = 4, Name = "Jennifer T. Tapia", Department = "Production", Position = "Manager" });

        stuff.Add(new Employee() { ID = 17, ParentID = 5, Name = "Judith P. Underhill", Department = "Finance", Position = "Manager" });
        stuff.Add(new Employee() { ID = 18, ParentID = 5, Name = "Russell E. Belton", Department = "Finance", Position = "Manager" });
        return stuff;
    }
}

MainWindow.xaml.cs

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

namespace WpfApplication1 {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
            grid.ItemsSource = Stuff.GetStuff();
        }

        private void SmartExpandNodes(int minChildCount) {
            TreeListNodeIterator nodeIterator = new TreeListNodeIterator(treeListView.Nodes, true);
            while (nodeIterator.MoveNext())
                nodeIterator.Current.IsExpanded = nodeIterator.Current.Nodes.Count >= minChildCount;
        }

        private void grid_Loaded(object sender, RoutedEventArgs e) {
            SmartExpandNodes(4);
        }
    }
}

MainWindow.xaml.vb

Imports Microsoft.VisualBasic
Imports System.Windows
Imports DevExpress.Xpf.Grid

Namespace WpfApplication1
    ''' <summary>
    ''' Interaction logic for MainWindow.xaml
    ''' </summary>
    Partial Public Class MainWindow
        Inherits Window
        Public Sub New()
            InitializeComponent()
            grid.ItemsSource = Stuff.GetStuff()
        End Sub

        Private Sub SmartExpandNodes(ByVal minChildCount As Integer)
            Dim nodeIterator As New TreeListNodeIterator(treeListView.Nodes, True)
            Do While nodeIterator.MoveNext()
                nodeIterator.Current.IsExpanded = nodeIterator.Current.Nodes.Count >= minChildCount
            Loop
        End Sub

        Private Sub grid_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
            SmartExpandNodes(4)
        End Sub
    End Class
End Namespace

Employees.vb

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic

Public Class Employee
    Private privateID As Integer
    Public Property ID() As Integer
        Get
            Return privateID
        End Get
        Set(ByVal value As Integer)
            privateID = value
        End Set
    End Property
    Private privateParentID As Integer
    Public Property ParentID() As Integer
        Get
            Return privateParentID
        End Get
        Set(ByVal value As Integer)
            privateParentID = value
        End Set
    End Property
    Private privateName As String
    Public Property Name() As String
        Get
            Return privateName
        End Get
        Set(ByVal value As String)
            privateName = value
        End Set
    End Property
    Private privatePosition As String
    Public Property Position() As String
        Get
            Return privatePosition
        End Get
        Set(ByVal value As String)
            privatePosition = value
        End Set
    End Property
    Private privateDepartment As String
    Public Property Department() As String
        Get
            Return privateDepartment
        End Get
        Set(ByVal value As String)
            privateDepartment = value
        End Set
    End Property
End Class

Public NotInheritable Class Stuff
    Private Sub New()
    End Sub
    Public Shared Function GetStuff() As List(Of Employee)
        Dim stuff As New List(Of Employee)()
        stuff.Add(New Employee() With {.ID = 1, .ParentID = 0, .Name = "Gregory S. Price", .Department = "", .Position = "President"})
        stuff.Add(New Employee() With {.ID = 2, .ParentID = 1, .Name = "Irma R. Marshall", .Department = "Marketing", .Position = "Vice President"})
        stuff.Add(New Employee() With {.ID = 3, .ParentID = 1, .Name = "John C. Powell", .Department = "Operations", .Position = "Vice President"})
        stuff.Add(New Employee() With {.ID = 4, .ParentID = 1, .Name = "Christian P. Laclair", .Department = "Production", .Position = "Vice President"})
        stuff.Add(New Employee() With {.ID = 5, .ParentID = 1, .Name = "Karen J. Kelly", .Department = "Finance", .Position = "Vice President"})

        stuff.Add(New Employee() With {.ID = 6, .ParentID = 2, .Name = "Brian C. Cowling", .Department = "Marketing", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 7, .ParentID = 2, .Name = "Thomas C. Dawson", .Department = "Marketing", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 8, .ParentID = 2, .Name = "Angel M. Wilson", .Department = "Marketing", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 9, .ParentID = 2, .Name = "Bryan R. Henderson", .Department = "Marketing", .Position = "Manager"})

        stuff.Add(New Employee() With {.ID = 10, .ParentID = 3, .Name = "Harold S. Brandes", .Department = "Operations", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 11, .ParentID = 3, .Name = "Michael S. Blevins", .Department = "Operations", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 12, .ParentID = 3, .Name = "Jan K. Sisk", .Department = "Operations", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 13, .ParentID = 3, .Name = "Sidney L. Holder", .Department = "Operations", .Position = "Manager"})

        stuff.Add(New Employee() With {.ID = 14, .ParentID = 4, .Name = "James L. Kelsey", .Department = "Production", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 15, .ParentID = 4, .Name = "Howard M. Carpenter", .Department = "Production", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 16, .ParentID = 4, .Name = "Jennifer T. Tapia", .Department = "Production", .Position = "Manager"})

        stuff.Add(New Employee() With {.ID = 17, .ParentID = 5, .Name = "Judith P. Underhill", .Department = "Finance", .Position = "Manager"})
        stuff.Add(New Employee() With {.ID = 18, .ParentID = 5, .Name = "Russell E. Belton", .Department = "Finance", .Position = "Manager"})
        Return stuff
    End Function
End Class

MainWindow.xaml (VB.NET)

<Window xmlns:dxg="clr-namespace:DevExpress.Xpf.Grid;assembly=DevExpress.Xpf.Grid.v11.1" x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
        dx:ThemeManager.ThemeName="Office2007Black"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <dxg:GridControl Name="grid" Loaded="grid_Loaded">
            <dxg:GridControl.Columns>
                <dxg:GridColumn FieldName="Name" />
                <dxg:GridColumn FieldName="Department" />
                <dxg:GridColumn FieldName="Position" />
            </dxg:GridControl.Columns>
            <dxg:GridControl.View>
                <dxg:TreeListView Name="treeListView" AutoWidth="True"
                                  KeyFieldName="ID" ParentFieldName="ParentID" />
            </dxg:GridControl.View>
        </dxg:GridControl>
    </Grid>
</Window>