Problem z rozwijaniem TreeView za pomocą kodu

private void button2_Click(object sender, EventArgs e)
        {

            foreach (TreeNode tn in tvMain.Nodes)
            {
                if (tn.Text == "Test1")
                {
                    tn.Expand();
                }

            }

                foreach (TreeNode tn2 in tvMain.Nodes[26].Nodes)
                {

                    if (tn2.Text == "Test2")
                    {
                        richTextBox1.Text += tn2.Text + "\n";
                        tn2.Expand();
                    }
                }   

        } 

private void tvMain_AfterExpand(object sender, System.Windows.Forms.TreeViewEventArgs e)
        {
            if (e.Node != null)
            {
                e.Node.Nodes.Clear();
                //e.Node.Nodes.Add(new TreeNode("Loading..."));

                int eventParentId = 0;

                if (e.Node != null)
                {
                    CSharpAPI6.betfair.api.global.BFEvent eventItem = (CSharpAPI6.betfair.api.global.BFEvent)e.Node.Tag;
                    eventParentId = eventItem.eventId;
                }

                GetEventAsyncRequest(eventParentId, e.Node).ToString();
                
            }
            //Expanded = true;
        } 

Application.DoEvents;

Application.DoEvents();

while (tvMain.Nodes[id].Nodes.Count > 20); //id - indeks wyższego węzła
break;
 

private IAsyncResult GetEventAsyncRequest(int eventParentId, TreeNode node)
        {
            // Get session from session manager
            string session = SessionTokenManager.GetSessionToken();

            // If no session, log in and get another one
            if (session == null)
            {
                session = MakeSession();
            }

            CSharpAPI6.betfair.api.global.GetEventsReq request = null;

            request = new CSharpAPI6.betfair.api.global.GetEventsReq();
            request.header = new CSharpAPI6.betfair.api.global.APIRequestHeader();
            request.header.sessionToken = session;
            request.eventParentId = eventParentId;

            var state = new CustomAsyncStateContainer(0, node, new object[] { eventParentId, node }, DateTime.Now);

            return simpleAPIWrapper.BFGlobalService.BegingetEvents(request, GetEventAsyncCallback, state);
        } 

private void DisplayGetEventTypes(CSharpAPI6.betfair.api.global.GetEventTypesResp resp, CustomAsyncStateContainer state)
        {
            // We need to display information from the provided API response
            tvMain.Nodes.Clear();

            if (resp.eventTypeItems != null)
            {
                CSharpAPI6.betfair.api.global.EventType[] eventItems = resp.eventTypeItems;

                int nodeCount = eventItems.Length;
                TreeNode[] nodes = new TreeNode[nodeCount];
                for (int i = 0; i < nodeCount; i++)
                {
                    CSharpAPI6.betfair.api.global.BFEvent eventItem = new CSharpAPI6.betfair.api.global.BFEvent();
                    eventItem.eventName = eventItems[i].name;
                    eventItem.eventId = eventItems[i].id;

                    nodes[i] = new TreeNode(eventItems[i].name);
                    nodes[i].Tag = eventItem;
                    nodes[i].Nodes.Add(new TreeNode("")); // Create a fake child node
                }
                tvMain.Nodes.AddRange(nodes);
            } 

public interface IAsyncResult
    {
        // Summary:
        //     Gets a user-defined object that qualifies or contains information about an
        //     asynchronous operation.
        //
        // Returns:
        //     A user-defined object that qualifies or contains information about an asynchronous
        //     operation.
        object AsyncState { get; }
        //
        // Summary:
        //     Gets a System.Threading.WaitHandle that is used to wait for an asynchronous
        //     operation to complete.
        //
        // Returns:
        //     A System.Threading.WaitHandle that is used to wait for an asynchronous operation
        //     to complete.
        WaitHandle AsyncWaitHandle { get; }
        //
        // Summary:
        //     Gets a value that indicates whether the asynchronous operation completed
        //     synchronously.
        //
        // Returns:
        //     true if the asynchronous operation completed synchronously; otherwise, false.
        bool CompletedSynchronously { get; }
        //
        // Summary:
        //     Gets a value that indicates whether the asynchronous operation has completed.
        //
        // Returns:
        //     true if the operation is complete; otherwise, false.
        bool IsCompleted { get; }
    } 

while (async.IsCompleted)
                break; 

public string MakeSession()
        {
            string session = null;
            var async = LoginAsyncRequest(simpleAPIWrapper.username, simpleAPIWrapper.password, simpleAPIWrapper.productId, simpleAPIWrapper.softwareId, null);

            int count = 0;
            while (!async.IsCompleted || !SessionTokenManager.HasSessions)
            {
                Thread.Sleep(500);

                if ((count++) == 20)
                {
                    throw new Exception("Time out occured in \"public string MakeSession()\"");
                }
            }
            session = SessionTokenManager.GetSessionToken();

            if (session == null)
            {
                throw new Exception("String session is NULL in \"public string MakeSession()\"");
            }

            return session;
        }