Adding new child-Node to specific parent-Node - vb.net

Question

I am trying to add a new child node into specific parent node.
The thing is that I can't find a property I could use to specify which parent Node I want to use.
Only I can use is:
TreeView1.SelectedNode.Nodes.Add(newNode)
But I don't want to use SelectedNode.
What I need should look like this:
TreeView1.ParentNode(Me.ds_Tables.Table.Rows(a).Item(0)).Nodes.Add(newNode)
edit:
So, I wrote ParentNode just to make it clear that that's a node where I will add a new node to.
Relationship between nodes and datatable is that I am using table column result to give a name to Node.
The thing is that my table looks like (id, code, name, parentId) parentId is the id column from that table. So, when parentId is filled (not Null) that means that that result is a part of another result from that table. (I hope that's clear for you, if it's not I'll try to explain in different way).
So, basically I have to find all results who has parentId filled and find which result own it and put that name into that "parent Node".

Answer 1

Option 1
It seems you read all the data at once at some point and then construct the tree. If that is the case, you can construct the TreeNodes fully before adding them to the TreeView:
Dim items As New List(Of Item)()
Dim map As New Dictionary(Of Integer, TreeNode)()
' first, create all TreeNode objects
For Each item As var In items
Dim node As New TreeNode()
' set node values
map.Add(item.Id, node)
Next
' second, construct the relations
For Each item As var In items
Dim node = map(item.Id)
If item.ParendID.HasValue Then
map(item.ParentID).Nodes.Add(node)
Else ' no parent = root node
TreeView.Nodes.Add(node)
End If
Next
Option 2
If your tree is dynamic, you can still keep a global dictionary indicating which Id links to which TreeNode:
Private map As New Dictionary(Of Integer, TreeNode)();
Option 3
Use the Tag property and write an Extension Method for TreeNodeCollection:
<System.Runtime.CompilerServices.Extension> _
Public Shared Function Find(nodes As TreeNodeCollection, item As Object) As TreeNode
For Each node As var In nodes
If node.Tag IsNot Nothing AndAlso node.Tag.Equals(item) Then
Return node
End If
Next
Return Nothing ' or throw an exception
End Function
and then use
TreeView.Nodes.Find(parentID).AddNodes(...)