Using Recursion to iterate through Treeview control

[dutsnekcirf]

I'm new to the concept of recursion and it's quite confusing to me. I found an article here on MSDN that talks about how to iterate through the nodes in a treeview. I've able to get the code example to work in my project, but rather than have it display a message box for each treenode, I'd like it to take the text property of each treenode and add it to an array.



Here's the code that I got:



Code Snippet

Private Sub ManningFiltersTreeView_AfterCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles ManningFiltersTreeView.AfterCheck
 
RecurseTree(ManningFiltersTreeView)
 
End Sub
 
Private Sub BuildArray(ByVal n As TreeNode)
 
MessageBox.Show(n.Text)
Dim aNode As TreeNode
For Each aNode In n.Nodes
BuildArray(aNode)
Next
 
End Sub
 
' Call the procedure using the top nodes of the treeview.
 
Private Sub RecurseTree(ByVal aTreeView As TreeView)
 
Dim n As TreeNode
For Each n In aTreeView.Nodes
BuildArray(n)
Next
 
End Sub
 

So basically where it says MessageBox.Show(n.Text), can I have it instead add the value of n.text to an array and then pass that back to my ManningFiltersTreeView_Aftercheck procedure?

[mldisibio]

Doing so will flatten the tree hierarchy into a single dimension array. Before a code suggestion is posted, is a flat array acceptable?

Or did you want a jagged array that mimics the node structure?

[mldisibio]

Assuming you are okay with a flattened hierarchy, this will do what you are looking for. Also notice that since both TreeView and TreeNode have a TreeNodeCollection, you can reduce your recursion to one method, which increases the readability a bit.

void ManningFiltersTreeView_AfterCheck(object sender, TreeViewEventArgs e){
 List<string> nodeTextList = new List<string>();
 ExtractTextFromNodes(ManningFiltersTreeView.Nodes, nodeTextList);
 string[] nodeTextArray = nodeTextList.ToArray();
}
static void ExtractTextFromNodes(TreeNodeCollection nodeList, List<string> buffer) {
 foreach (TreeNode n in nodeList) {
  buffer.Add(n.Text);
  ExtractTextFromNodes(n.Nodes, buffer);
  }
}
 

Full example:

using System;
using System.Collections.Generic;
using System.Windows.Forms;
 
namespace bytes {
  class test {
 
    static void Main() {
      TreeView myFamilyTree = createTreeView();
      List<string> familyList = new List<string>();
      ExtractTextFromNodes(myFamilyTree.Nodes, familyList);
      string[] familyArray = familyList.ToArray();
      Console.WriteLine(String.Join(Environment.NewLine, familyArray));
    }
 
    static void ExtractTextFromNodes(TreeNodeCollection nodeList, List<string> buffer) {
      foreach (TreeNode n in nodeList) {
        buffer.Add(n.Text);
        ExtractTextFromNodes(n.Nodes, buffer);
      }
    }
 
    static TreeView createTreeView() {
      TreeView tempTree = new TreeView();
      tempTree.BeginUpdate();
      tempTree.Nodes.Add("Grandfather");
      tempTree.Nodes[0].Nodes.Add("Father");
      tempTree.Nodes[0].Nodes.Add("Uncle");
      tempTree.Nodes[0].Nodes[0].Nodes.Add("Grandchild1 By Father");
      tempTree.Nodes[0].Nodes[0].Nodes.Add("Grandchild2 By Father");
      tempTree.Nodes[0].Nodes[1].Nodes.Add("Grandchild3 By Uncle");
      tempTree.Nodes[0].Nodes[1].Nodes.Add("Grandchild4 By Uncle");
      tempTree.Nodes[0].Nodes[0].Nodes[1].Nodes.Add("GreatGrandchild1 By Grandchild2");
      tempTree.Nodes[0].Nodes[1].Nodes[0].Nodes.Add("GreatGrandchild2 By Grandchild3");
      tempTree.EndUpdate();
      return tempTree;
    }
  }
}
 

Will someone post the VB version please, since I don't have a VB.Net test environment.

Mike

[mldisibio]

Friend Class test
  ' Methods
  Private Shared Sub Main()
      Dim myFamilyTree As TreeView = test.createTreeView
      Dim familyList As New List(Of String)
      test.ExtractTextFromNodes(myFamilyTree.Nodes, familyList)
      Dim familyArray As String() = familyList.ToArray
      Console.WriteLine(String.Join(Environment.NewLine, familyArray))
  End Sub
  Private Shared Sub ExtractTextFromNodes(ByVal nodeList As TreeNodeCollection, ByVal buffer As List(Of String))
      Dim n As TreeNode
      For Each n In nodeList
          buffer.Add(n.Text)
          test.ExtractTextFromNodes(n.Nodes, buffer)
      Next
  End Sub
  Private Shared Function createTreeView() As TreeView
      Dim tempTree As New TreeView
      tempTree.BeginUpdate
      tempTree.Nodes.Add("Grandfather")
      tempTree.Nodes.Item(0).Nodes.Add("Father")
      tempTree.Nodes.Item(0).Nodes.Add("Uncle")
      tempTree.Nodes.Item(0).Nodes.Item(0).Nodes.Add("Grandchild1 By Father")
      tempTree.Nodes.Item(0).Nodes.Item(0).Nodes.Add("Grandchild2 By Father")
      tempTree.Nodes.Item(0).Nodes.Item(1).Nodes.Add("Grandchild3 By Uncle")
      tempTree.Nodes.Item(0).Nodes.Item(1).Nodes.Add("Grandchild4 By Uncle")
      tempTree.Nodes.Item(0).Nodes.Item(0).Nodes.Item(1).Nodes.Add("GreatGrandchild1 By Grandchild2")
      tempTree.Nodes.Item(0).Nodes.Item(1).Nodes.Item(0).Nodes.Add("GreatGrandchild2 By Grandchild3")
      tempTree.EndUpdate
      Return tempTree
  End Function
End Class
 

[dutsnekcirf]

Great! I did want a flattened array, I will use the array as my Criteria1: property in the Range.Autofilter method in an Excel Spreadsheet.

I haven't given your code a test yet since I'm not at work but will do so once I'm in.

Thanks for your reply.

[dutsnekcirf]

I LOVE you guys!!!!! It's working. It's taken me a month to get it working right and with your help it's finally working perfectly.

I originally had it working with just checkboxes in a control group, but this treeview code has taken my code from 500 and something lines of code down to something like 30 lines of code including comments.

Thank you, Thank you, Thank you.