问C# 4.0中的异步函数调用

EN

 public async void checkConnect()
    {
        for (int i = 0; i < treeView1.Nodes.Count; i++)
        {
            string result = await Task.Factory.StartNew<string>(() => connectTread(), TaskCreationOptions.LongRunning);
        }
    }

public string connectTread()
    {
        string ret = "";
        string[] IpHERE;

        foreach (TreeNode child in treeView1.Nodes)
        {
            IpHERE = child.Text.Split(' ');
            Modbus mb = new Modbus();
            Regex regIP = new Regex(@"\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b");

            if (regIP.IsMatch(IpHERE[1]) && IpHERE[1].Length != 0 && IpHERE[4].Length != 0 && IpHERE[9].Length != 0 && IpHERE[11].Length != 0 && (mb.OpenTCP(IpHERE[1], IpHERE[4], IpHERE[9], IpHERE[11])))
            {
                child.SelectedImageIndex = 3;

                mb.CloseTCP();
                ret = "Ok";
            }
            else
            {
                child.SelectedImageIndex = 4;
                ret = "Error";
            }
        }
        return ret;
    }