Question

I want to be able to create a tree view that can get its nodes form a directory on a computer. In the code below, I am able to get all of the files into a list, but I cannot get the folder correct. What I mean is in your user directory, you have sub directorys such as, Documents, Music, and Pictures. When you run this code, it displays them each as thier own node, not nested. I hope this makes sense. Thanks In VB.NET please.

     Private Sub PopulateTree(ByVal path As String, ByVal subfoldercount As Integer)

         Dim items() As String
         items = Directory.GetFileSystemEntries(path)
         Dim itm As String

         TreeVeiw1.Nodes.Add(path)
         Dim currentnode As TreeNode = TreeView1.Nodes.Item(0)
         For Each itm In items
             If Directory.Exists(itm) Then
                 Dim nodeOjb As New TreeNode
                 nodeOjb.Text = "FOLDER :: " & subfoldercount & " :: " & itm
                 nodeOjb.ForeColor = Color.Blue
                 currentnode.Nodes.Add(nodeOjb)
                 PopulateTree(itm, subfoldercount + 1)
             Else
                 Dim nodeOjb As New TreeNode
                 nodeOjb.Text = "FILE :: " & subfoldercount & " :: " & itm
                 Select Case My.Computer.FileSystem.GetFileInfo(itm).Extension
                     Case ".txt"
                         nodeOjb.ForeColor = Color.Orange
                         currentnode.Add(nodeOjb)
                     Case ".png"
                         nodeOjb.ForeColor = Color.Red
                         currentnode.Add(nodeOjb)
                    Case ".ico"
                         nodeOjb.ForeColor = Color.Green
                         currentnode.Add(nodeOjb)
                    Case ".url"
                         nodeOjb.ForeColor = Color.Black
                         currentnode.Add(nodeOjb)
                 End Select
             End If
         Next

     End Sub

Changed the code to the way spinion told me to. When I run this code I get an error ‘Object reference not set to an instance of an object’ when it starts to try and add files to the tree view.

Answer 1

Just from a quick glance it seems that you are adding every node you find to the root level of the tree.

TreeView1.Nodes.Add(nodeOjb)

What you should be doing is passing through with the recursive call the current node you are working on and use that to add the next level of nodes found.

currentNode.Add(nodeObj)

This way you can have children added to nodes. Rather than always adding all nodes to the root of the tree.

EDIT: Here is the changes you need to make to the PopulateTree method:

Private Sub PopulateTree(currentNode As TreeNode, path__1 As String, subfoldercount As Integer)
    Dim items As String() = Nothing
    items = Directory.GetFileSystemEntries(path__1)

    Dim nodeParent As TreeNodeCollection = If((currentNode IsNot Nothing), currentNode.Nodes, Me.TreeView1.Nodes)

    For Each itm As String In items
        If Directory.Exists(itm) Then
            Dim nodeOjb = New TreeNode()
            nodeOjb.Text = "FOLDER :: " & subfoldercount & " :: " & itm
            nodeOjb.ForeColor = Color.Blue
            nodeParent.Add(nodeOjb)
            Me.PopulateTree(nodeOjb, itm, subfoldercount + 1)
        Else
            Dim nodeOjb = New TreeNode()
            nodeOjb.Text = "FILE :: " & subfoldercount & " :: " & itm
            Select Case Path.GetExtension(itm)
                Case ".txt"
                    nodeOjb.ForeColor = Color.Orange
                    nodeParent.Add(nodeOjb)
                    Exit Select
                Case ".png"
                    nodeOjb.ForeColor = Color.Red
                    nodeParent.Add(nodeOjb)
                    Exit Select
                Case ".ico"
                    nodeOjb.ForeColor = Color.Green
                    nodeParent.Add(nodeOjb)
                    Exit Select
                Case ".url"
                    nodeOjb.ForeColor = Color.Black
                    nodeParent.Add(nodeOjb)
                    Exit Select
            End Select
        End If
    Next
End Sub

Then when you call it for the first time you do so like this:

PopulateTree(Nothing, "", 0)

You pass a empty reference for the first call so it uses the parent. The second parameter is your path.

p.s. I am primarily a C# guy so I used a converter to change the code over. It should work but you might need to tweak a little.