问如何捕获异步HttpClient调用中的所有异常？

EN

    static bool myFunction(int nmsTimeout, out string strOutErrDesc)
    {
        //'nmsTimeout' = timeout in ms for connection
        //'strOutErrDesc' = receives error description as string
        bool bRes = false;
        strOutErrDesc = "";

        HttpClient httpClient = null;
        System.Threading.Tasks.Task<string> tsk = null;

        try
        {
            httpClient = new HttpClient();
            tsk = httpClient.GetStringAsync("https://website-to-connet.com");

            if (tsk.Wait(nmsTimeout))
            {
                if (tsk.Status == System.Threading.Tasks.TaskStatus.RanToCompletion)
                {
                    string strRes = tsk.Result;
                    strRes = strRes.Trim();

                    if (!string.IsNullOrWhiteSpace(strRes))
                    {
                        bRes = true;
                    }
                    else
                    {
                        //Empty result
                        strOutErrDesc = "Empty result";
                    }
                }
                else
                {
                    //Bad task completion
                    strOutErrDesc = "Bad completion result: " + tsk.Status.ToString();
                }
            }
            else
            {
                //Timed out
                strOutErrDesc = "Timeout expired: " + nmsTimeout + " ms.";
            }
        }
        catch (Exception ex)
        {
            //Error
            strOutErrDesc = "Exception: " + ex.Message;
            if (tsk != null)
            {
                strOutErrDesc += " -- ";
                int c = 1;
                foreach(var exc in tsk.Exception.InnerExceptions)
                {
                    strOutErrDesc += c.ToString() + ". " + exc.InnerException.Message;
                }
            }

            bRes = false;
        }

        return bRes;
    }