递归ASP.NET树视图填充中的StackOverflowException

Question

I have a custom ASP.NET treeview control, which uses existing MS Treeview. I create and recreate the treeview upon postbacks (it is in UpdatePanel) from a stored IEnumerable.

Some items are added like this:

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack && !Page.IsAsync)
        {
            DD.Items = null;

            DD.Items.Add(new TreeviewItem("Choice 1", "4", "-1"));// = items;
            DD.Items.Add(new TreeviewItem("something", "1", "-1"));
            DD.Items.Add(new TreeviewItem("Europe", "2", "-1"));
            DD.Items.Add(new TreeviewItem("pff", "3", "-1"));
}}

The control is initialized and loaded in it's OnLoad using BuildTreeFromItemCollection():

    public void BuildTreeFromItemCollection()
    {
        BuildTreeFromItemCollection(this.Items, null);
    }

    public void BuildTreeFromItemCollection(IEnumerable<StoredItem> items, TreeNode parentNode)
    {

        IEnumerable<TreeviewItem> tvItems = items.Cast<TreeviewItem>();
        var nodes = tvItems.Where(x => parentNode == null ? int.Parse(x.Parent) <= 0 : x.Parent == parentNode.Value);

        TreeNode childNode;
        foreach (var i in nodes)
        {
            childNode = new TreeNode(i.Name, i.Value)
            {
                PopulateOnDemand = this.PopulateOnDemand
            };

            if (parentNode == null)
            {
                TvHierarchy.Nodes.Add(childNode);
            }
            else
            {
                parentNode.ChildNodes.Add(childNode);
            }

            this.BuildTreeFromItemCollection(items, childNode);
        } 
    }

TreeNodePopulate is handled like so:

    void TvHierarchy_TreeNodePopulate(object sender, TreeNodeEventArgs e)
    {

        this.EnsureChildControls();

        IEnumerable<StoredItem> childItems = NodePopulator(e.Node.Value);
        foreach (StoredItem item in childItems)
        {
            TreeNode newNode = new TreeNode(item.Name, item.Value);
            newNode.PopulateOnDemand = this.PopulateOnDemand;
            e.Node.ChildNodes.Add(newNode);
        }

        this.Items.AddRange(childItems);
    }

and this Func is temporarily attached to the NodePopulator:

    private IEnumerable<StoredItem> ItemLoader(string val)
    {
        List<StoredItem> itemList = new List<StoredItem>();
        Random r = new Random();

        for (int i = 0; i <= 4; i++)
        {
            int rand = r.Next(10,100);
            itemList.Add(new TreeviewItem("test " + rand.ToString(), rand.ToString(), val));
        }

        return itemList;
    }

Unfortunately the BuildTreeFromItemCollection falls into infinite loop after a couple of node expansions, around 4th level, and i'm left with stack overflow.

The exact exception shows up on the line

var nodes = tvItems.Where(x => parentNode == null ? int.Parse(x.Parent) <= 0 : x.Parent == parentNode.Value);

but the Call stack looks already filled up. Where's the problem?

Answer 1

So it seems that the whole problem was in the code generating new nodes in this test function:

int rand = r.Next(10,100);
itemList.Add(new TreeviewItem("test " + rand.ToString(), rand.ToString(), val));

So when an ID was generated which already was earlier the code went into infinite loop. After expanding range to (10,10000) everything works fine.