我怎样才能从异步方法button_ClickEvent得到一个字符串 [英] How can I get a string in a button_ClickEvent from async method

问题描述

我的家伙，我有以下code：

I guys I have the following code:

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;
    } 

我使用这个功能的一些方法（例如）

I use this functions some method(for example)

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

我的问题是：如果我想获得 buttonclick结果（对象发件人，EventArgs五）我该怎么办

我也试过，但这么想的工作：

I have tried this but dosen't work:

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

修改

我已经解决了的私人和无效的，并添加等待添加问题异步 在登录（BLA BLA）

I' ve solved the problem adding async between private and void and adding await before login(bla bla)

推荐答案

而下面是一个显而易见的解决方案，它具有隐蔽捕获：

While the following is an obvious solution, it has hidden catches:

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

• 如果登录抛出异常？它会去不可观测，很可能会导致应用程序崩溃。


• 如果用户点击一个按钮两次，而previous异步登录操作已经在进行什么？你肯定不想要两个悬而未决的登录。


• What if login throws an exception? It will go unobserved and most likely will crash the application.
• What if user clicks a button twice, while the previous async login operation is already in progress? You certainly don't want two pending logins.

下面是一个稍微改进过的版本：

Here's a slightly improved version:

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;
}

这篇关于我怎样才能从异步方法button_ClickEvent得到一个字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！