XPO - How to implement self-referenced persistent objects and display them within the XtraTreeList

This example demostrates how to implement self-referenced persistent objects and display them within the XtraTreeList. A simple example of a self-referenced object is an Employee. An employee reports to a Manager, but at the same time, this employee might also be a manager for other employers, referred to as Subordinates.

A self-referenced object has a parent object property and a child collection. Here is the persistent Employee class. It has a Manager property of type Employee and Subordinates of type XPCollection<Employee>. Both properties are decorated with the Association attribute. As such, the Employee type appears on both sides of a one-to-many association.

using DevExpress.Xpo;  

public class Employee : XPObject {  
    public Employee(Session session) : base(session) { }  

    string _FullName;  
    public string FullName {  
        get { return _FullName; }  
        set { SetPropertyValue("FullName", ref _FullName, value); }  
    }  

    private string _Title;  
    public string Title {  
        get { return _Title; }  
        set { SetPropertyValue("Title", ref _Title, value); }  
    }  

    Employee _Manager;  
    [Association("ManagerSubordinates")]  
    public Employee Manager {  
        get { return _Manager; }  
        set { SetPropertyValue("Manager", ref _Manager, value); }  
    }  

    [Association("ManagerSubordinates")]  
    public XPCollection<Employee> Subordinates {  
        get { return GetCollection<Employee>("Subordinates"); }  
    }  
}

Imports DevExpress.Xpo  

Public Class Employee  
    Inherits XPObject  
    Public Sub New(ByVal session As Session)  
        MyBase.New(session)  
    End Sub  

    Private _FullName As String  
    Public Property FullName() As String  
        Get  
            Return _FullName  
        End Get  
        Set(ByVal value As String)  
            SetPropertyValue("FullName", _FullName, value)  
        End Set  
    End Property  

    Private _Title As String  
    Public Property Title() As String  
        Get  
            Return _Title  
        End Get  
        Set(ByVal value As String)  
            SetPropertyValue("Title", _Title, value)  
        End Set  
    End Property  

    Private _Manager As Employee  
    <Association("ManagerSubordinates")> _  
    Public Property Manager() As Employee  
        Get  
            Return _Manager  
        End Get  
        Set(ByVal value As Employee)  
            SetPropertyValue("Manager", _Manager, value)  
        End Set  
    End Property  

    <Association("ManagerSubordinates")> _  
    Public ReadOnly Property Subordinates() As XPCollection(Of Employee)  
        Get  
            Return GetCollection(Of Employee)("Subordinates")  
        End Get  
    End Property  
End Class

A collection of self-referenced objects can be displayed in the XtraTreeList. TreeList properties must be set as shown below.
C#

treeList1.KeyFieldName = "This";  
treeList1.ParentFieldName = "Manager!";  
treeList1.RootValue = null;  
treeList1.DataSource = xpCollection1;

treeList1.KeyFieldName = "This"  
treeList1.ParentFieldName = "Manager!"  treeList1.RootValue = Nothing  
treeList1.DataSource = xpCollection1

Files to Review

Employee.cs (VB: Employee.vb)
Form1.cs (VB: Form1.vb)

Documentation

More Examples

Specifics of binding to properties of type persistent object

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