Object not set to an instance error on first select of treenode only

[MarkGB]

I've been struggling with this for a while and finally gave in and am seeking some help.

The below runs on a `After Select` event in a treeview. The code runs absolutely fine but since I've made a slight adjustment to the process I'm getting an `Object not set to an instance of an object` error the first time the node is clicked. Once the error has been cleared the code runs as normal.

The error gets triggered on this line

Dim NodeFile As New IO.DirectoryInfo(Path.Combine(tempMail, tvProgress.SelectedNode.FullPath))

Like I say, once I've cleared the error the code runs absolutely fine.

      Try
            Dim da As New OleDb.OleDbDataAdapter("", "")
            Dim dt As New DataTable
            Dim aClients As String = My.Settings.ClientDB
            Dim conn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & aClients & ""
            Dim n As Integer
            Dim q As Integer
            Dim tempMail As String = My.Settings.Temporary
            Dim enUK As New CultureInfo("en-GB")

            lstFiles.Enabled = True
            lstFiles.Items.Clear()

            If (e.Node.Level) > 0 Then

                If e.Node.Parent.Text = "Archive" Then Call INIDate()

                If ndes.Contains(tvProgress.SelectedNode.Text) Then
                    For n = 0 To UBound(AllDetails)

                        Dim Datey As String = Nothing
                        If e.Node.Parent.Text <> "Archive" Then
                            Datey = Date.ParseExact(Convert.ToDateTime(e.Node.Parent.Text), "dd/MM/yy", enUK)
                        Else

                            For q = 0 To UBound(INIdet)
                                If e.Node.Parent.Text = "Archive" Then Datey = INIdet(q).iDate


                                Dim code As String = AllDetails(n).uCode
                                Dim op As String = AllDetails(n).uOps
                                Dim name As String = AllDetails(n).uName
                                Dim dte As String = Date.Parse(Datey).ToString("dd-MM-yyyy")

                                If e.Node.Text = name & " - " & code & " - " & op Then

                                    Dim txt2check As String = My.Settings.FileStream & code & "-" & op & "-" & dte & ".txt"
                                    If Not File.Exists(txt2check) Then
                                        Dim tw As StreamWriter = File.CreateText(My.Settings.FileStream & code & "-" & op & "-" & dte & ".txt") ' Create a file to write to. 
                                        tw.WriteLine("unitname=" & AllDetails(n).uName)
                                        tw.WriteLine("unitcode=" & AllDetails(n).uCode)
                                        tw.WriteLine("opername=" & AllDetails(n).uOps)
                                        tw.WriteLine("plandate=" & Datey)
                                        tw.Flush()
                                        tw.Close()
                                        Call TxtRfrsh()
                                        Call RfshArray()
                                    End If
                                End If
                            Next
                        End If


                        If AllDetails(n).uName & " - " & AllDetails(n).uCode & " - " & AllDetails(n).uOps & " - " & AllDetails(n).uPlan = e.Node.Text & " - " & Datey Then
                            Dim fldr As String = My.Settings.FileStream & AllDetails(n).uFile
                            With fldr
                                If My.Computer.FileSystem.DirectoryExists(fldr) Then

                                    Directory.Delete(fldr, True)
                                End If
                            End With


                            Application.DoEvents()

                            Dim NodeFile As New IO.DirectoryInfo(Path.Combine(tempMail, tvProgress.SelectedNode.FullPath))

                            Dim reports = NodeFile.EnumerateFiles().Select(Function(f) Path.GetFileName(f.Name)).ToList()

                            Dim newreport As String = String.Join("' AND Documents.DocName <> '", reports.ToArray())

                            If tvProgress.Nodes.Count = 0 Then Exit Sub

                            Dim eSearch As String = AllDetails(n).uCode
                            Dim fSearch As String = AllDetails(n).uOps
                            Dim gsearch As String = "'" & newreport & "'"

                            da.SelectCommand.Connection.ConnectionString = conn
                            da.SelectCommand.CommandText = "SELECT Documents.DocName FROM Documents WHERE (Documents.UnitCode = ?) AND (Documents.OpName = ?) AND (Documents.DocName <> " & gsearch & ") AND Documents.Required = True ORDER BY DocName"
                            da.SelectCommand.Parameters.AddWithValue("@p1", eSearch)
                            da.SelectCommand.Parameters.AddWithValue("@p2", fSearch)
                            da.Fill(dt)

                            dt.Rows.Add("Add Additional Requirement")
                            lstRequired.DataSource = dt
                            lstRequired.DisplayMember = "DocName"
                            lstRequired.Refresh()

                            Dim tFiles As String = My.Settings.LTFile
                            Dim dl As DataTable = CType(lstRequired.DataSource, DataTable)
                            Using sR = New IO.StreamReader(tFiles & UCase("ProgExcluded.txt"))
                                While (sR.Peek() > -1)
                                    Dim rows() = dl.Select("DocName = '" + sR.ReadLine + "'")
                                    For Each row In rows
                                        row.Delete()
                                    Next
                                    dl.AcceptChanges()
                                End While
                            End Using
                        End If
                    Next


                End If
            End If
            Exit Sub

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

Cross-posted here http://stackoverflow.com/questions/2...-treenode-only

[kaliman79912]

Put a breakpoint in that line and when it stops, look at the values of tempMail and tvProgress, one of those is empty.

[MarkGB]

Thanks, tried that and its the tvProgress.SelectedNode.FullPath which is empty. Don't quite understand as the path exists?

[kaliman79912]

It should be the way you are assigning the object to tvProgress, if that object has not been set, it does not mater if the Path Exists

[ident]

Your code needs some serious re writing, firstly getting rid of the doevents. You even checking My.Settings.Temporary has a value?

[ident]

Wrapping the whole code in a Try block is not exactly a good idea also.

[MarkGB]

I'm just learning with this. I've removed both suggestions from ident. I am aware that the code could be written far better but this is a first attempt so I'm just finding my feet and this works for me at the moment. I'm struggling to understand how I'm assigning the object to tvprogress incorrectly though.

I'll keep on reading and trying

[kaliman79912]

On second thought, it must be the selected object, not the tvprogress

[ident]

Put a break point on Dim tempMail As String = My.Settings.Temporary whats the value?

[MarkGB]

It gives the directory C:\working.

As kaliman79912 suggested with his location of a Breakpoint its the tvprogress.selectednode.fullpath thats empty. Once the error is suppressed and the node reselected the code operates properly.

This error only happens if the text file (text2check) has to be created from a date located in an .INI file and falls under the parent Node 'Archive'