public string ExpandStateFieldName { get; set; }

Public Property ExpandStateFieldName As String

<dxg:GridControl ItemsSource="{Binding Employees}">
    <dxg:GridControl.View>
        <dxg:TreeListView KeyFieldName="ID" 
                          ParentFieldName="ParentID" 
                          ExpandStateFieldName="Expanded"/>
    </dxg:GridControl.View>
    <!-- columns -->
</dxg:GridControl>

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 bool Expanded { get; set; }
}

Public Class Employee
    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
    Public Property Expanded As Boolean
End Class