How to Group by Name in Treeview Control - vb.net

Question

I have been googling and searching youtube but find no answer, so I would like to ask for help in here.
I want to group the name in the TreeView control in VB, how can I do it?
Thank you
Public Class FrmPengingat
Private Sub FrmPengingat_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'DSLap.PengingatHutang' table. You can move, or remove it, as needed.
Me.PengingatHutangTableAdapter.Fill(Me.DSLap.PengingatHutang)
'fill the tree control
Dim NmPemasok As String
Dim NoNota As String
Dim TglJatuhTempo As Date
Dim Total As Decimal
Dim tmpNmPemasok As String
Dim i As Integer
For i = 0 To DSLap.PengingatHutang.Count - 1
NmPemasok = DSLap.PengingatHutang.Rows(i).Item(0)
tmpNmPemasok = DSLap.PengingatHutang.Rows(i).Item(0)
NoNota = DSLap.PengingatHutang.Rows(i).Item(1)
TglJatuhTempo = DSLap.PengingatHutang.Rows(i).Item(2)
Total = DSLap.PengingatHutang.Rows(i).Item(3)
TreeView1.Nodes.Add(i, NmPemasok).Nodes.Add(i, NoNota & " (" & TglJatuhTempo & ") " & Total)
Next
End Sub
End Class

Answer 1

This line:
TreeView1.Nodes.Add(i, NmPemasok).Nodes.Add(i, NoNota & " (" & TglJatuhTempo & ") " & Total)
adds a new parent node every time. You should check if the tree view already contains a node with the same text and only add a new one if it doesn't.
I suggest you make the key the same as the text for the parent node, that way it'll be easier to check if it exists or not.
Replace the above with this:
If TreeView1.Nodes.ContainsKey(NmPemasok) Then 'The parent node already exists.
TreeView1.Nodes(NmPemasok).Nodes.Add(i, NoNota & " (" & TglJatuhTempo & ") " & Total)
Else 'The parent node doesn't exist.
TreeView1.Nodes.Add(NmPemasok, NmPemasok).Nodes.Add(i, NoNota & " (" & TglJatuhTempo & ") " & Total)
End If