Filter TreeView with all nodes and childs

Question

I have a parent node which has a child, and this child has another child etc.. and they are all in a TreeView

So I create a global variable to save all my nodes as:

private TreeNodeCollection ProjectTreeView { get; set; }

Then I set data of the tree node into my global variable:

ProjectTreeView = this.tvProjectList.Nodes[0].Nodes;

And When I click a button I want to filter my TreeView, so first I clear the TreeView, then I iterate over the collection and only show the nodes that meet my condition:

private void rdoIssued_Click(object sender, EventArgs e)
{
    //blocks repainting tree till all objects loaded
    this.tvProjectList.BeginUpdate();
    this.tvProjectList.Nodes.Clear();

    foreach (TreeNode projectNode in ProjectTreeView)
    {
        if (bool.Parse(projectNode.Tag.ToString().Split('|')[8]) == true)
        {
            this.tvProjectList.Nodes.Add((TreeNode)projectNode.Clone());
        }

    }

    //enables redrawing tree after all objects have been added
    this.tvProjectList.EndUpdate();
}

The problem is it only clone the first Node but not the children. How can I clone a node with all children?

Answer 1

Doing the opposite is much easier. You could iterate through all the nodes to keep the filtered nodes and remove the rest. First, create a backup for the 0-level nodes.

public partial class YourForm : Form
{
    public YourForm()
    {
        InitializeComponent();
        //...

        BackUpTree();
    }

    private List<TreeNode> ProjectTreeView = new List<TreeNode>();

    private void BackUpTree()
    {
        if (ProjectTreeView.Count == 0)
            foreach (TreeNode tn in tvProjectList.Nodes)
                ProjectTreeView.Add(tn.Clone() as TreeNode);
    }

Create a method to reset the original tree:

    private void ResetTree(bool expandAll = false)
    {
        tvProjectList.BeginUpdate();
        tvProjectList.Nodes.Clear();

        foreach (var tn in ProjectTreeView)
            tvProjectList.Nodes.Add(tn.Clone() as TreeNode);

        if (expandAll) tvProjectList.ExpandAll();
        tvProjectList.EndUpdate();
    }

Iterator function to get all the nodes:

    private IEnumerable<TreeNode> GetAllNodes(TreeNodeCollection Nodes)
    {
        foreach (TreeNode tn in Nodes)
        {
            yield return tn;

            foreach (TreeNode child in GetAllNodes(tn.Nodes))
                yield return child;
        }
    }

... and a method to do the filter part:

    private void FilterTree(bool expandAll = false)
    {
        ResetTree(); // <- comment if you are doing multiple filters...
        tvProjectList.BeginUpdate();

        //.Reverse() is required here to iterate backward because the collections
        //are modified when removing nodes. You can call .ToList() instead to 
        //iterate forward.
        foreach (var node in GetAllNodes(tvProjectList.Nodes).Reverse())
        {
            if (bool.Parse(projectNode.Tag.ToString().Split('|')[8]) == false)
                if (node.Parent is null)
                    tvProjectList.Nodes.Remove(node);
                else
                    node.Parent.Nodes.Remove(node);
        }

        if (expandAll) tvProjectList.ExpandAll();
        tvProjectList.EndUpdate();
    }
}