c# - 如何从异步方法中获取 button_ClickEvent 中的字符串

Question

伙计们，我有以下代码:

public static CookieContainer cookies;
public static HttpWebRequest GetNewRequest(string targetUrl, CookieContainer SessionCookieContainer)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(targetUrl);
        request.CookieContainer = SessionCookieContainer;
        request.AllowAutoRedirect = false;
        return request;
    }
    public async static Task<HttpWebResponse> MakeRequest(HttpWebRequest request, CookieContainer SessionCookieContainer, Dictionary<string, string> parameters = null)
    {
        HttpWebResponse response;
        request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.52 Safari/536.5Accept: */*";
        request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
        request.CookieContainer = SessionCookieContainer;
        request.AllowAutoRedirect = false;
        if (parameters != null)
        {
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            string s = "";
            foreach (KeyValuePair<string, string> pair in parameters)
            {
                if (s.Length == 0)
                {
                    s = s + string.Format("{0}={1}", pair.Key, pair.Value);
                }
                else
                {
                    s = s + string.Format("&{0}={1}", pair.Key, pair.Value);
                }
            }
            byte[] bytes = Encoding.UTF8.GetBytes(s);
            using (Stream stream = await request.GetRequestStreamAsync())
            {
                stream.Write(bytes, 0, bytes.Length);
            }
        }
        request.Method = "GET";
        response = await request.GetResponseAsync() as HttpWebResponse;
        SessionCookieContainer.Add(response.Cookies);
        while (response.StatusCode == HttpStatusCode.Found)
        {
            response.Close();
            request = GetNewRequest(response.Headers["Location"], SessionCookieContainer);
            response = await request.GetResponseAsync() as HttpWebResponse;
            SessionCookieContainer.Add(response.Cookies);
        }
        return response;
    } 

我使用这个函数的一些方法(例如)

async Task<string> login(string url, string id, string pw)
    {
       ///code...
    }

我的问题是:如果我想在 buttonclick(object sender, EventArgs e) 中得到结果我该怎么办？

我已经试过了，但是没有用:

private void buttonclick(object sender, EventArgs e)
{
    string htmlPage=login(url, id, pw);
}

编辑

我已经解决了添加 async 的问题在 private 之间无效并添加await之前login(bla bla)

Answer 1

虽然以下是一个显而易见的解决方案，但它有隐藏的问题:

private async void buttonclick(object sender, EventArgs e)
{
    string htmlPage = await login(url, id, pw);
}

• 如果 login 抛出异常怎么办？它不会被观察到，很可能会使应用程序崩溃。
• 如果用户点击一个按钮两次，而之前的异步登录操作已经在进行中怎么办？您当然不希望有两个待处理的登录。

这是一个稍微改进的版本:

Task<string> _pendingLogin = null;
private async void buttonclick(object sender, EventArgs e)
{
    if (_pendingLogin != null)
    {
        MessageBox.Show("Login pending...");
        return;
    }

    try
    {
        _pendingLogin = login(url, id, pw);
        string htmlPage = await _pendingLogin;
        MessageBox.Show("Logged in: " + htmlPage);
    }
    catch(Exception ex)
    {
        MessageBox.Show("Error in login: " + ex.Message);
    }

    _pendingLogin = null;
}