TreeNodeCollection reference problem

Question

First off we have the almighty code!

List nodes = new List();
TreeNode Temp = new TreeNode();

TreeNodeCollection nodeList = treeViewTab4DirectoryTree.Nodes;

while (nodeList.Count != 0)
{
    Temp = nodeList[0];

    while (Temp.FirstNode != null)
    {
        Temp = Temp.FirstNode;
    }

    if (!nodes.Contains(Temp.FullPath))
    {
        nodes.Add(Temp.Text);
    }

    nodeList.Remove(Temp);
}

Now the problem: I have written the code above with the intent of creating a List containing the text from all the nodes in the tree. That works perfectly. The problem I am having is when I remove the nodes from my variable they are also being removed from the actual list. The question would be how can I make a copy of the list of nodes so I can play with them without messing with the ACTUAL list. How do I make a copy of it without just making a reference to it? Any help will be greatly appreciated!

Answer 1

Your problem arises because "nodeList" is a reference to treeViewTab4DirectoryTree.Nodes, rather than a copy of it.

The solution depends entirely on the what type of TreeNodeCollection you're using (WinForms, ASP.net, something else?), as you'll need to look for a .Copy(), .Clone(), .ToArray() method or similar to take a copy of the contents of the collection, rather than a reference to the existing collection.

If, for example, you're using asp.net and thus the System.Web.UI.WebControls.TreeNodeCollection, you could use the .CopyTo method in a way similar to this:

TreeNode[] x = null;
treeViewTab4DirectoryTree.Nodes.CopyTo(x, 0);

Answer 2

@Arne

I have the same problem. Although almost the same...

I have a treeview with nodes. I want to keep a copy of the original nodes before editing. After I made a copy i delete a subnode, but it is also deleted in my array. Strange?

Any idea??

Code:

    public Form1()
    {
        InitializeComponent();
    }

    private TreeNode[] _storeArray;
    private List<TreeNode> _storeList;

    private void Form1_Load(object sender, EventArgs e)
    {
        FillTreeview();

        Console.WriteLine("In store: " + _storeArray[1].Nodes.Count);
        Console.WriteLine("In original: " + _storeList[1].Nodes.Count);
    }

    private void FillTreeview()
    {
        TreeNode newNode = new TreeNode();
        newNode.Text = "RootNode 1";
        newNode.Nodes.Add("SubNode 1");
        newNode.Nodes.Add("SubNode 2");
        newNode.Nodes.Add("SubNode 3");
        newNode.Nodes.Add("SubNode 4");

        treeView1.Nodes.Add(newNode);

        TreeNode newNode2 = new TreeNode("RootNode 2");
        newNode2.Nodes.Add("SubNode 1");
        newNode2.Nodes.Add("SubNode 2");
        newNode2.Nodes.Add("SubNode 3");

        treeView1.Nodes.Add(newNode2);

        _storeArray = new TreeNode[treeView1.Nodes.Count];
        treeView1.Nodes.CopyTo(_storeArray, 0);

        _storeList = new List<TreeNode>();
        _storeList.AddRange(_storeArray);

        treeView1.BeginUpdate();

        // Delete subnodes
        for (int i = treeView1.Nodes[1].Nodes.Count - 1; i >= 0; i--)
        {
            treeView1.Nodes[1].Nodes.RemoveAt(i);
        }

        treeView1.EndUpdate();

    }