Dim conn As OleDbConnection = New OleDbConnection
conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Server=ИЛЬЯ-ПК\SQLEXPRESS; Database=Akvaponika;Integrated Security=SSPI;"
conn.Open()
Dim cmd As OleDbCommand = conn.CreateCommand
cmd.CommandText = "SELECT * FROM tree2"
Dim rdr As OleDbDataReader = cmd.ExecuteReader
TreeView1.Nodes.Clear()
Dim FindedNodes(0) As TreeNode
Dim ID As String = ""
Dim ParentID As String = ""
Dim KOI As String = ""
Do
While rdr.Read()
ID = rdr.Item(0).ToString
ParentID = rdr.Item(1).ToString
KOI = rdr.Item(2).ToString

If ParentID Is String.Empty Then
TreeView1.Nodes.Add(ID, KOI) ' add parent 
Else
FindedNodes = TreeView1.Nodes.Find(ParentID, True)
FindedNodes(0).Nodes.Add(ID, KOI)
End If

End While
Loop While rdr.NextResult()

TreeView1.EndUpdate()
TreeView1.ExpandAll()

conn.Close()