using DevExpress.XtraTreeList;
using DevExpress.XtraTreeList.Nodes;

private void InitializeComponent() {
   // ...
   this.treeList1 = new MyTreeList();
   // ...
}

private void Form1_Load(object sender, System.EventArgs e) {
   // ...
   ((MyTreeListNode)treeList1.Nodes[0]).Height = 25;
   // ...
}

public class MyTreeList : TreeList {
   protected override TreeListNode CreateNode(int nodeID, TreeListNodes owner) {
      return new MyTreeListNode(nodeID, owner);
   }
   protected override void InternalNodeChanged(TreeListNode node, NodeChangeTypeEnum changeType) {
      if(changeType == NodeChangeTypeEnum.User1)
         LayoutChanged();
      base.InternalNodeChanged(node, changeType);
   }
   protected override void RaiseCalcNodeHeight(TreeListNode node, ref int nodeHeight) {
      MyTreeListNode myNode = node as MyTreeListNode;
      if(myNode != null)
         nodeHeight = myNode.Height;
      else
         base.RaiseCalcNodeHeight(node, ref nodeHeight);
   }
   public virtual int DefaultNodesHeight { get { return 18; } }
}
public class MyTreeListNode : TreeListNode {
   const int minHeight = 5;
   int height;
   public MyTreeListNode(int id, TreeListNodes owner) : base(id, owner) {
      this.height = (owner.TreeList as MyTreeList).DefaultNodesHeight;
   }
   public int Height {
      get { return height; }
      set {
         if(Height == value || value < minHeight) return;
         height = value;
         Changed(NodeChangeTypeEnum.User1);
      }
   }
}

Imports DevExpress.XtraTreeList
Imports DevExpress.XtraTreeList.Nodes

<System.Diagnostics.DebuggerStepThrough()>Private Sub InitializeComponent()
   Me.TreeList1 = New MyTreeList()
   ' ...
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
   ' ...
   CType(TreeList1.Nodes(0), MyTreeListNode).Height = 25
   ' ...
End Sub
End Class

Public Class MyTreeList
Inherits TreeList
Protected Overrides Function CreateNode(ByVal nodeID As Integer, ByVal owner As TreeListNodes) As TreeListNode
   Return New MyTreeListNode(nodeID, owner)
End Function
Protected Overrides Sub InternalNodeChanged(ByVal node As TreeListNode, ByVal changeType As NodeChangeTypeEnum)
   If changeType = NodeChangeTypeEnum.User1 Then
      LayoutChanged()
   End If
   MyBase.InternalNodeChanged(node, changeType)
End Sub
Protected Overrides Sub RaiseCalcNodeHeight(ByVal node As TreeListNode, ByRef nodeHeight As Integer)
   Dim myNode As MyTreeListNode = CType(node, MyTreeListNode)
   If Not myNode Is Nothing Then
      nodeHeight = myNode.Height
   Else
      MyBase.RaiseCalcNodeHeight(node, nodeHeight)
   End If
End Sub
Public Overridable ReadOnly Property DefaultNodesHeight() As Integer
   Get
      Return 18
   End Get
End Property
End Class

Public Class MyTreeListNode
Inherits TreeListNode
Const minHeight As Integer = 5
Dim fHeight As Integer
Public Sub New(ByVal id As Integer, ByVal owner As TreeListNodes)
   MyBase.New(id, owner)
   Me.fHeight = CType(owner.TreeList, MyTreeList).DefaultNodesHeight
End Sub
Public Property Height() As Integer
   Get
      Return fHeight
   End Get
   Set(ByVal Value As Integer)
      If fHeight = Value Or Value < minHeight Then Return
      fHeight = Value
      Changed(NodeChangeTypeEnum.User1)
   End Set
End Property
End Class