TreeViewControl.ChildNodesSelector Property

Gets or sets a selector that returns the list of child nodes for the processed node. This is a dependency property.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v20.2.dll

NuGet Packages: DevExpress.WindowsDesktop.Wpf.Grid.Core, DevExpress.Wpf.Grid.Core

Declaration

C#

public IChildNodesSelector ChildNodesSelector { get; set; }

VB.NET

Public Property ChildNodesSelector As IChildNodesSelector

Property Value

Type	Description
DevExpress.Xpf.Grid.IChildNodesSelector	The child nodes selector.

Remarks

The Child Nodes Selector returns node children. You can use this approach to create a hierarchical data structure for different object types.

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 DevExpress.Xpf.Grid.IChildNodeSelector, and override the SelectChildren 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>