c# - WebResponse 不返回任何 cookie

Question

我目前正在研究一个帮助我创建带有 cookie 和 POST 参数的 WebRequest 的类。但是 response.cookies 总是空的。我如何获取返回的 cookie 并将它们与下一个请求一起发送？

class WebHandler
{
    private string lasturl = "";
    private Dictionary<string, Cookie> cookies;
    public string lastContent;

    public WebHandler()
    {
        cookies = new Dictionary<string, Cookie>();
    }

    public HttpWebResponse request(string address)
    {
        lasturl = address;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);
        foreach (KeyValuePair<string, Cookie> pair in this.cookies)
        {
            Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
            request.CookieContainer.Add(pair.Value);
        }
        request.Method = "GET";
        if(lasturl != "")
            request.Referer = lasturl;

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        foreach (Cookie newCookie in response.Cookies)
        {
            Console.WriteLine(" new cookie: " + newCookie.Name + " = " + newCookie.Value);
            this.cookies[newCookie.Name] = newCookie;
        }
        lastContent = new StreamReader(response.GetResponseStream()).ReadToEnd();
        return response;
    }

    public HttpWebResponse request(string address, Dictionary<string, string> postParameters)
    {
        lasturl = address;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);
        foreach (KeyValuePair<string, Cookie> pair in this.cookies)
        {
            Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
            request.CookieContainer.Add(pair.Value);
        }
        request.Method = "POST";

        string postData = "";
        foreach (string key in postParameters.Keys)
            postData += HttpUtility.UrlEncode(key) + "=" + HttpUtility.UrlEncode(postParameters[key]) + "&";


        byte[] data = Encoding.ASCII.GetBytes(postData);
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = data.Length;
        Stream requestStream = request.GetRequestStream();
        requestStream.Write(data, 0, data.Length);
        requestStream.Close();

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        foreach (Cookie newCookie in response.Cookies)
        {
            Console.WriteLine(" new cookie: " + newCookie.Name + " = " + newCookie.Value);
            this.cookies[newCookie.Name] = newCookie;
        }
        lastContent = new StreamReader(response.GetResponseStream()).ReadToEnd();
        return response;
    }
}

Answer 1

因为 this.cookies 最初是空的，你的代码永远不会进入循环

foreach (KeyValuePair<string, Cookie> pair in this.cookies)
{
     Console.WriteLine(" Sent cookie: " + pair.Value.Name + " = " + pair.Value.Value);
     request.CookieContainer.Add(pair.Value);
}

它的坏部分是您永远不会看到 request.CookieContainer 为 null(否则您会得到 null 引用异常)，这会告诉您有问题。

由于 request.CookieContainer 为空，HttpWebResponse 永远不会获取返回的 cookie。

解决方案:简单，只需添加

if (request.CookieContainer == null) 
         request.CookieContainer = new CookieContainer();

之后

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(address);

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PS:您可能想阅读 this question关于 c# 中的命名约定。

PS2:在方法 request 中使用变量名 request 不会提高可读性。