Private Sub Main_Load(ByVal sender As System.Object, ByVal e As _
    System.EventArgs) Handles MyBase.Load
        initilizeFillTreeView()
    End Sub
 
    Public Sub initilizeFillTreeView()
        Dim con As New OleDb.OleDbConnection
        Dim cmd_Obj As New OleDb.OleDbCommand
        Dim cmd_mv As New OleDb.OleDbCommand
        Dim cmd_tx As New OleDb.OleDbCommand
        Dim cmd_rb As New OleDb.OleDbCommand
        Dim reader_Obj As OleDb.OleDbDataReader
        Dim reader_mv As OleDb.OleDbDataReader
        Dim reader_tx As OleDb.OleDbDataReader
        Dim reader_rb As OleDb.OleDbDataReader
        Dim list(1000, 2) As String
 
        con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data" & _
          "Source=|DataDirectory|\datenbank.mdb"
        cmd_Obj.Connection = con
        cmd_mv.Connection = con
        cmd_tx.Connection = con
        cmd_rb.Connection = con
        cmd_Obj.CommandText = "select * from Objekte"
 
        Dim i, j, mv, tx, tx_level As Integer
 
        Dim tr As New TreeView()
        tr.Dock = DockStyle.Fill
        Try
            con.Open()
            reader_Obj = cmd_Obj.ExecuteReader()
            Do While reader_Obj.Read()
                i = i + 1
                list(i, 1) = reader_Obj("Obj_name")
                list(i, 2) = reader_Obj("Obj_ID")
            Loop
            con.Close()
            For j = 1 To i
                tx_level = 0
                tr.Nodes.Add(list(j, 1))
                tr.Nodes(j - 1).Nodes.Add("Übersicht")
                tx_level = tx_level + 1
                'Prüfen auf aktiven Mietvertrag 
                cmd_mv.CommandText = "Select * from Mietvertrag where" & _
                  "MV_Status= 'Aktiv' AND MV_Objekt_ID= " & list(j, 2) & ""
                con.Open()
                reader_mv = cmd_mv.ExecuteReader()
                Do While reader_mv.Read()
                    mv = mv + 1
                Loop
                If mv > 0 Then
                    tr.Nodes(j - 1).Nodes.Add("Mietvertrag")
                    tx_level = tx_level + 1
                End If
                con.Close()
 
                'Transaktionen nach jahr Gruppieren
                cmd_tx.CommandText = "SELECT Year(TX_Datum) AS TXJahr," & _
                  "TX_Objekt_ID FROM Transaktionen GROUP BY Year(" & _
                  "TX_Datum),TX_Objekt_ID HAVING (TX_Objekt_ID= " & list(j, 2) _
                  & "); "
                con.Open()
                reader_tx = cmd_tx.ExecuteReader()
                tx = 0
                Do While reader_tx.Read()
                    tx = tx + 1
                    If tx = 1 Then
                        tr.Nodes(j - 1).Nodes.Add("Transaktionen")
                    End If
                    tr.Nodes(j - 1).Nodes(tx_level).Nodes.Add(reader_tx( _
                      "TXJahr"))
                Loop
                con.Close()
 
                'Regelbuchungen prüfen
                cmd_rb.CommandText = "SELECT * FROM Regelbuchungen Where" & _
                  "RB_Objekt_ID= " & list(j, 2) & "; "
                con.Open()
                reader_rb = cmd_tx.ExecuteReader()
                tx = 0
                Do While reader_rb.Read()
                    tx = tx + 1
                    If tx = 1 Then
                        tr.Nodes(j - 1).Nodes.Add("Regelbuchungen")
                    End If
                Loop
                con.Close()
            Next j
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
        Obj_tree.Controls.Add(tr)
    End Sub
 
 
    Private Sub Obj_tree_NodeMouseClick(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.TreeNodeMouseClickEventArgs) Handles _
      Obj_tree.NodeMouseClick
        txt_Obj_Name_selected.Text = e.Node.Text()
    End Sub