TreeViewControl.TreeDerivationMode Property

Gets or sets the tree derivation mode. This is a dependency property.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v23.2.dll

NuGet Package: DevExpress.Wpf.Grid.Core

Declaration

C#

public TreeDerivationMode TreeDerivationMode { get; set; }

VB.NET

Public Property TreeDerivationMode As TreeDerivationMode

Property Value

Type	Default	Description
TreeDerivationMode	ChildNodesSelector	The tree derivation mode.

Available values:

Name	Description
Selfreference	Builds a tree from a self-referential data structure. To learn more, see Bind to Self-Referential Data Structure.
ChildNodesSelector	You should manually write code to specify where a data object’s child items come from by creating a selector class. To learn more, see Bind to Hierarchical Data Structure.
HierarchicalDataTemplate	Builds a tree using Hierarchical Data Templates. To learn more, see Hierarchical Data Templates.

Remarks

The TreeViewControl can display information in a tree from a self-referential (flat) or hierarchical data structure. The TreeDerivationMode property specifies the corresponding tree derivation modes for each data structure:

Data Structure Type	Tree Derivation Mode
Self-Referential (Flat)	Self-Reference
Hierarchical	Child Nodes Selector Child Nodes Path Hierarchical Data Template

ChildNodesSelector

The Child Nodes Selector returns node children. You can use the returned list of child nodes to create a hierarchical data structure for different object types.

Use the Child Nodes Selector to create a hierarchical data structure in the TreeViewControl. An example of this structure is shown below:

C#

public class ProjectObject : BaseObject {
    public ObservableCollection<ProjectStage> Stages { get; set; }
}

public class ProjectStage : BaseObject {
    public ObservableCollection<Task> Tasks { get; set; }
}

public class Task : BaseObject {
    State state;
    // ...
}

VB.NET

Public Class ProjectObject
    Inherits BaseObject

    Public Property Stages As ObservableCollection(Of ProjectStage)
End Class

Public Class ProjectStage
    Inherits BaseObject

    Public Property Tasks As ObservableCollection(Of Task)
End Class

Public Class Task
    Inherits BaseObject

    Private state As State
    ' ...
End Class 

1. Create a selector class that implements IChildNodesSelector, and override the SelectChildren(Object) method that returns node children.

   For the Project-Stage-Task class structure, the selector class is as follows:

   C#

   public class CustomChildrenSelector : IChildNodesSelector {
       public IEnumerable SelectChildren(object item) {
           if (item is Task)
               return null;
           else if (item is ProjectStage)
               return (item as ProjectStage).Tasks;
           else if (item is ProjectObject)
               return (item as ProjectObject).Stages;
           return null;
       }
   }
   

   VB.NET

   Public Class CustomChildrenSelector
       Inherits IChildNodesSelector
   
       Public Function SelectChildren(ByVal item As Object) As IEnumerable
           If TypeOf item Is Task Then
               Return Nothing
           ElseIf TypeOf item Is ProjectStage Then
               Return (TryCast(item, ProjectStage)).Tasks
           ElseIf TypeOf item Is ProjectObject Then
               Return (TryCast(item, ProjectObject)).Stages
           End If
   
           Return Nothing
       End Function
   End Class
   

2. Assign the Child Nodes Selector to the ChildNodesSelector property.

   XAML

   <dxg:TreeViewControl ItemsSource="{Binding DataItems}" 
                        TreeViewFieldName="Name">
       <dxg:TreeViewControl.ChildNodesSelector>
           <local:CustomChildrenSelector/>
       </dxg:TreeViewControl.ChildNodesSelector>
   </dxg:TreeViewControl>
   

ChildNodesPath

Use the Child Nodes Path to bind the TreeViewControl to a collection if all objects have the same field that contains child nodes.

In this mode, you can use the HasChildNodesPath property to control whether a node has children.

To build a tree structure, set the ChildNodesPath property to a field that contains child nodes (the Employees field in the code sample below).

XAML

<dxg:TreeViewControl ItemsSource="{Binding EmployeeDepartments}" 
                     ChildNodesPath="Employees" 
                     TreeViewFieldName="Name"
                     HasChildNodesPath="HasChildNodes"/>

C#

using System.Windows;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using DevExpress.Mvvm;

namespace TreeViewChildNodesSelector {
    public class MainWindowViewModel : ViewModelBase {
        public MainWindowViewModel() {
            EmployeeDepartments = Departments.GetDepartments();
        }
        public List<EmployeeDepartment> EmployeeDepartments { get; set; }
    }
    public class Employee {
        public Employee(int id, string name) {
            ID = id;
            Name = name;
        }
        public int ID { get; set; }
        public string Name { get; set; }
    }
    public class EmployeeDepartment {
        public string Name { get; set; }
        public ObservableCollection<Employee> Employees { get; }
        public bool HasChildNodes { get; set; }

        public EmployeeDepartment(string name, IEnumerable<Employee> employees) {
            Name = name;
            Employees = new ObservableCollection<Employee>(employees);
        }
    }
    public static class Departments {
        public static List<EmployeeDepartment> GetDepartments() {
            List<EmployeeDepartment> departments = new List<EmployeeDepartment> {
                new EmployeeDepartment("Management", new Employee[] {
                new Employee(0, "Gregory S. Price")
                }, true),
                new EmployeeDepartment("Marketing", new Employee[] {
                new Employee(1, "Irma R. Marshall"),
                new Employee(2, "Brian C. Cowling"),
                new Employee(3, "Thomas C. Dawson"),
                new Employee(4, "Bryan R. Henderson"),
                }, true),
                new EmployeeDepartment("Operations", new Employee[] {
                new Employee(5, "John C. Powell"),
                new Employee(6, "Harold S. Brandes"),
                new Employee(7, "Jan K. Sisk"),
                new Employee(8, "Sidney L. Holder"),
                }, true),
                new EmployeeDepartment("Production", new Employee[] {
                new Employee(9, "Christian P. Laclair"),
                new Employee(10, "James L. Kelsey"),
                new Employee(11, "Howard M. Carpenter"),
                new Employee(12, "Jennifer T. Tapia"),
                },false),
                new EmployeeDepartment("Finance", new Employee[] {
                new Employee(13, "Karen J. Kelly"),
                new Employee(14, "Judith P. Underhill"),
                new Employee(15, "Russell E. Belton"),
                },false)
            };
            return departments;
        }
    }
}

VB.NET

Imports System.Windows
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
Imports DevExpress.Mvvm

Namespace TreeViewChildNodesSelector
    Public Class MainWindowViewModel
        Inherits ViewModelBase

        Public Sub New()
            EmployeeDepartments = Departments.GetDepartments()
        End Sub

        Public Property EmployeeDepartments As List(Of EmployeeDepartment)
    End Class

    Public Class Employee
        Public Sub New(ByVal id As Integer, ByVal name As String)
            ID = id
            Name = name
        End Sub

        Public Property ID As Integer
        Public Property Name As String
    End Class

    Public Class EmployeeDepartment
        Public Property Name As String
        Public ReadOnly Property Employees As ObservableCollection(Of Employee)
        Public Property HasChildNodes As Boolean

        Public Sub New(ByVal name As String, ByVal employees As IEnumerable(Of Employee))
            Name = name
            Employees = New ObservableCollection(Of Employee)(employees)
        End Sub
    End Class

    Module Departments
        Function GetDepartments() As List(Of EmployeeDepartment)
            Dim departments As List(Of EmployeeDepartment) = New List(Of EmployeeDepartment) From {
                New EmployeeDepartment("Management", New Employee() {New Employee(0, "Gregory S. Price")}, True),
                New EmployeeDepartment("Marketing", New Employee() {New Employee(1, "Irma R. Marshall"), New Employee(2, "Brian C. Cowling"), New Employee(3, "Thomas C. Dawson"), New Employee(4, "Bryan R. Henderson")}, True),
                New EmployeeDepartment("Operations", New Employee() {New Employee(5, "John C. Powell"), New Employee(6, "Harold S. Brandes"), New Employee(7, "Jan K. Sisk"), New Employee(8, "Sidney L. Holder")}, True),
                New EmployeeDepartment("Production", New Employee() {New Employee(9, "Christian P. Laclair"), New Employee(10, "James L. Kelsey"), New Employee(11, "Howard M. Carpenter"), New Employee(12, "Jennifer T. Tapia")}, False),
                New EmployeeDepartment("Finance", New Employee() {New Employee(13, "Karen J. Kelly"), New Employee(14, "Judith P. Underhill"), New Employee(15, "Russell E. Belton")}, False)
            }
            Return departments
        End Function
    End Module
End Namespace

Selfreference

Set the TreeDerivationMode property to Selfreference to enable the self-referential mode.

To build a tree structure, your data source should contain the following two fields with the same data type:

• Key Field - This field should contain unique values used to identify nodes. Assign its name to the KeyFieldName property.
• Parent Field - This field should contain values that indicate parent nodes. Assign its name to the ParentFieldName property.

In this mode, you can specify the RootValue property to add to the collection of root nodes only nodes with the specified parent field value.

XAML

<dxg:TreeViewControl ItemsSource="{Binding Employees}" 
                     TreeDerivationMode="Selfreference"
                     KeyFieldName="ID" 
                     ParentFieldName="ParentID" 
                     TreeViewFieldName="Name">
    <dxg:TreeViewControl.RootValue>
        <sys:Int32>1</sys:Int32>
    </dxg:TreeViewControl.RootValue>
</dxg:TreeViewControl>

C#

using System.Windows;
using System.Collections.Generic;
using DevExpress.Mvvm;

namespace TreeViewSelfreference {
    public class Employee : BindableBase {
        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 Staff {
        public static List<Employee> GetStaff() {
            List<Employee> staff = new List<Employee> {
                new Employee() { ID = 1, ParentID = 0, Name = "Gregory S. Price", Department = "", Position = "President" },
                new Employee() { ID = 2, ParentID = 1, Name = "Irma R. Marshall", Department = "Marketing", Position = "Vice President" },
                new Employee() { ID = 3, ParentID = 1, Name = "John C. Powell", Department = "Operations", Position = "Vice President" },
                new Employee() { ID = 4, ParentID = 1, Name = "Christian P. Laclair", Department = "Production", Position = "Vice President" },
                new Employee() { ID = 5, ParentID = 1, Name = "Karen J. Kelly", Department = "Finance", Position = "Vice President" },
                new Employee() { ID = 6, ParentID = 2, Name = "Brian C. Cowling", Department = "Marketing", Position = "Manager" },
                new Employee() { ID = 7, ParentID = 2, Name = "Thomas C. Dawson", Department = "Marketing", Position = "Manager" },
                new Employee() { ID = 8, ParentID = 2, Name = "Angel M. Wilson", Department = "Marketing", Position = "Manager" },
                new Employee() { ID = 9, ParentID = 2, Name = "Bryan R. Henderson", Department = "Marketing", Position = "Manager" },
                new Employee() { ID = 10, ParentID = 3, Name = "Harold S. Brandes", Department = "Operations", Position = "Manager" },
                new Employee() { ID = 11, ParentID = 3, Name = "Michael S. Blevins", Department = "Operations", Position = "Manager" },
                new Employee() { ID = 12, ParentID = 3, Name = "Jan K. Sisk", Department = "Operations", Position = "Manager" },
                new Employee() { ID = 13, ParentID = 3, Name = "Sidney L. Holder", Department = "Operations", Position = "Manager" },
                new Employee() { ID = 14, ParentID = 4, Name = "James L. Kelsey", Department = "Production", Position = "Manager" },
                new Employee() { ID = 15, ParentID = 4, Name = "Howard M. Carpenter", Department = "Production", Position = "Manager" },
                new Employee() { ID = 16, ParentID = 4, Name = "Jennifer T. Tapia", Department = "Production", Position = "Manager" },
                new Employee() { ID = 17, ParentID = 5, Name = "Judith P. Underhill", Department = "Finance", Position = "Manager" },
                new Employee() { ID = 18, ParentID = 5, Name = "Russell E. Belton", Department = "Finance", Position = "Manager" }
            };
            return staff;
        }
    }
    public class MainWindowViewModel : ViewModelBase {
        public MainWindowViewModel() {
            Employees = Staff.GetStaff();
        }
        public List<Employee> Employees { get; private set; }
    }
}

VB.NET

Imports System.Windows
Imports System.Collections.Generic
Imports DevExpress.Mvvm

Namespace TreeViewSelfreference
    Public Class Employee
        Inherits BindableBase

        Public Property ID As Integer
        Public Property ParentID As Integer
        Public Property Name As String
        Public Property Position As String
        Public Property Department As String
    End Class

    Module Staff
        Function GetStaff() As List(Of Employee)
            Dim staff As List(Of Employee) = New List(Of Employee) From {
                New Employee() With { .ID = 1, .ParentID = 0, .Name = "Gregory S. Price", .Department = "", .Position = "President" },
                New Employee() With { .ID = 2, .ParentID = 1, .Name = "Irma R. Marshall", .Department = "Marketing", .Position = "Vice President" },
                New Employee() With { .ID = 3, .ParentID = 1, .Name = "John C. Powell", .Department = "Operations", .Position = "Vice President" },
                New Employee() With { .ID = 4, .ParentID = 1, .Name = "Christian P. Laclair", .Department = "Production", .Position = "Vice President" },
                New Employee() With { .ID = 5, .ParentID = 1, .Name = "Karen J. Kelly", .Department = "Finance", .Position = "Vice President" },
                New Employee() With { .ID = 6, .ParentID = 2, .Name = "Brian C. Cowling", .Department = "Marketing", .Position = "Manager" },
                New Employee() With { .ID = 7, .ParentID = 2, .Name = "Thomas C. Dawson", .Department = "Marketing", .Position = "Manager" },
                New Employee() With { .ID = 8, .ParentID = 2, .Name = "Angel M. Wilson", .Department = "Marketing", .Position = "Manager" },
                New Employee() With { .ID = 9, .ParentID = 2, .Name = "Bryan R. Henderson", .Department = "Marketing", .Position = "Manager" },
                New Employee() With { .ID = 10, .ParentID = 3, .Name = "Harold S. Brandes", .Department = "Operations", .Position = "Manager" },
                New Employee() With { .ID = 11, .ParentID = 3, .Name = "Michael S. Blevins", .Department = "Operations", .Position = "Manager" },
                New Employee() With { .ID = 12, .ParentID = 3, .Name = "Jan K. Sisk", .Department = "Operations", .Position = "Manager" },
                New Employee() With { .ID = 13, .ParentID = 3, .Name = "Sidney L. Holder", .Department = "Operations", .Position = "Manager" },
                New Employee() With { .ID = 14, .ParentID = 4, .Name = "James L. Kelsey", .Department = "Production", .Position = "Manager" },
                New Employee() With { .ID = 15, .ParentID = 4, .Name = "Howard M. Carpenter", .Department = "Production", .Position = "Manager" },
                New Employee() With { .ID = 16, .ParentID = 4, .Name = "Jennifer T. Tapia", .Department = "Production", .Position = "Manager" },
                New Employee() With { .ID = 17, .ParentID = 5, .Name = "Judith P. Underhill", .Department = "Finance", .Position = "Manager" },
                New Employee() With { .ID = 18, .ParentID = 5, .Name = "Russell E. Belton", .Department = "Finance", .Position = "Manager" }
            }
            Return staff
        End Function
    End Module

    Public Class MainWindowViewModel
        Inherits ViewModelBase

        Public Sub New()
            Employees = Staff.GetStaff()
        End Sub

        Public Property Employees As List(Of Employee)
    End Class
End Namespace

HierarchicalDataTemplate

You can use templates to create a hierarchical data structure in the TreeViewControl. An example of this structure is shown below:

C#

public class ProjectObject : BaseObject {
    public ObservableCollection<ProjectStage> Stages { get; set; }
}

public class ProjectStage : BaseObject {
    public ObservableCollection<Task> Tasks { get; set; }
}

public class Task : BaseObject {
    State state;
    // ...
}

VB.NET

Public Class ProjectObject
    Inherits BaseObject

    Public Property Stages As ObservableCollection(Of ProjectStage)
End Class

Public Class ProjectStage
    Inherits BaseObject

    Public Property Tasks As ObservableCollection(Of Task)
End Class

Public Class Task
    Inherits BaseObject

    Private state As State
    ' ...
End Class 

If all objects have the same field that contains child nodes, create a hierarchical data template and assign it to the NodeTemplate property. You can put hierarchical data templates into resources. Specify the data type to which a template should be applied:

XAML

<Window.Resources>
    <HierarchicalDataTemplate DataType="{x:Type local:ProjectObject}" ItemsSource="{Binding Path=Stages}" />
    <HierarchicalDataTemplate DataType="{x:Type local:ProjectStage}" ItemsSource="{Binding Path=Tasks}" />
</Window.Resources>

<dxg:TreeViewControl ItemsSource="{Binding DataItems}" 
                     TreeViewFieldName="Name" 
                     TreeDerivationMode="HierarchicalDataTemplate"/>

If all objects have different fields that contain child nodes:

1. Create a template selector that implements the System.Windows.Controls.DataTemplateSelector and overrides the SelectTemplate method.

   XAML

   <Window.Resources>
       <ResourceDictionary>
           <local:CustomHierarchicalDataTemplateSelector x:Key="selector">
               <local:CustomHierarchicalDataTemplateSelector.ProjectDataTemplate>
                   <HierarchicalDataTemplate ItemsSource="{Binding Path=Stages}" />
               </local:CustomHierarchicalDataTemplateSelector.ProjectDataTemplate>
               <local:CustomHierarchicalDataTemplateSelector.ProjectStageDataTemplate>
                   <HierarchicalDataTemplate ItemsSource="{Binding Path=Tasks}" />
               </local:CustomHierarchicalDataTemplateSelector.ProjectStageDataTemplate>
           </local:CustomHierarchicalDataTemplateSelector>
       </ResourceDictionary>
   </Window.Resources>
   

   C#

   public class CustomHierarchicalDataTemplateSelector : DataTemplateSelector {
   
       public HierarchicalDataTemplate ProjectDataTemplate { get; set; }
       public HierarchicalDataTemplate ProjectStageDataTemplate { get; set; }
   
       public override System.Windows.DataTemplate SelectTemplate(object item, System.Windows.DependencyObject container) {
           var rowData = item as DevExpress.Xpf.Grid.TreeList.TreeListRowData;
           var element = rowData.Row;
           if (element is ProjectObject)
               return ProjectDataTemplate;
           if (element is ProjectStage)
               return ProjectStageDataTemplate;
           return null;
       }
   }
   

   VB.NET

   Public Class CustomHierarchicalDataTemplateSelector
       Inherits DataTemplateSelector
   
       Public Property ProjectDataTemplate As HierarchicalDataTemplate
       Public Property ProjectStageDataTemplate As HierarchicalDataTemplate
   
       Public Overrides Function SelectTemplate(ByVal item As Object, ByVal container As System.Windows.DependencyObject) As System.Windows.DataTemplate
           Dim rowData = TryCast(item, DevExpress.Xpf.Grid.TreeList.TreeListRowData)
           Dim element = rowData.Row
           If TypeOf element Is ProjectObject Then Return ProjectDataTemplate
           If TypeOf element Is ProjectStage Then Return ProjectStageDataTemplate
           Return Nothing
       End Function
   End Class
   

2. Assign the template selector to the NodeTemplateSelector property.

3. Set the TreeDerivationMode property to HierarchicalDataTemplate.

   XAML

   <dxg:TreeViewControl TreeDerivationMode="HierarchicalDataTemplate"
                        NodeTemplateSelector="{StaticResource selector}"/>
   

Refer to the following help topic for more information: Hierarchical Data Structure.