credentials - 具有凭据的 WebClient 仍未下载文件

Question

我正在尝试使用用户名/密码从网站下载文件。您需要为注册帐户付费才能下载文件 - 我们已经做到了。我正在尝试传递用户名/密码并按如下方式下载文件:

if (docUrl != null)
            {
                if (!string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password))
                    this.WebClientInstance.Credentials = new NetworkCredential(username, password);

                fileData = this.WebClientInstance.DownloadData(docUrl);
                this.WebClientInstance.Dispose();
                isDataDownloaded = true;
            }

WebClientInstance 是一个 System.Net.WebClient。我调试并验证了它是否正在设置凭据。我没有下载 PDF，而是得到了一个 HTML 页面，提示我登录以访问该文件。我已验证用户名/密码正确。我使用相同的凭据与 WatiN 一起抓取网站。

还有什么我应该在这里做的吗？

更新

好的，我四处搜寻了一下，找到了一些关于这个问题的有用信息。我还没有让它工作，但我想我更接近了。首先，您需要创建一个扩展 WebClient 类的 cookie 感知 WebClient，如下所示:

public class CookiesAwareWebClient : WebClient
{
    public CookieContainer CookieContainer { get; private set; }

    public CookiesAwareWebClient()
    {
        this.CookieContainer = new CookieContainer();
    }

    protected override WebRequest GetWebRequest(Uri address)
    {
        var webRequest = base.GetWebRequest(address);

        if (webRequest is HttpWebRequest)
            (webRequest as HttpWebRequest).CookieContainer = this.CookieContainer;

        return webRequest;
    }
}

接下来是使用WebClient.UploadValues()方法将登录信息上传到目标网站。目标资源鉴权和下载的完整流程如下:

using (var webClient = new CookiesAwareWebClient())
                    {
                        var postData = new NameValueCollection()
                        {
                            { "userId", username },
                            { "password", password }
                        };

                        webClient.UploadValues(docUrl, postData);

                        fileData = webClient.DownloadData(docUrl);
                    }

我对网站使用表单验证的看法是错误的。它是一个 JSP 网站并使用 JSESSIONID。我已经验证我正在取回一个 cookie，其中似乎是一个有效的 32 字节 JSESSIONID 值。

但是，当我调用 WebClient.DownloadData() 时，它仍然只返回重定向的登录页面。我试图通过将 HttpWebRequest 上的 AllowAutoRedirect 属性设置为 false 来解决此问题，但随后它返回 0 个字节。

还有什么我需要做的，这样它就不会重定向，并且会在我通过身份验证后将我带到该资源吗？

Answer 1

(在问题编辑中回答。转换为社区维基答案。参见 Question with no answers, but issue solved in the comments (or extended in chat))

OP 写道:

Solved. So the problem was between my ears. I was passing in the URL for the secure resource to the .UploadValues() method, knowing that it would redirect to the login page. However, I really needed to pass in the URL from the login form (where it goes upon submitting) - not the login page itself. Once I did that, it worked correctly. I think I'm going to go find a career in food service now.

LINKS

There were already a few questions posted on SO that addressed this issue. I just didn't know what I was looking for at first so I didn't see those... Anywhere here are a couple good resources that I came across when working on this issue:

how to maintaine cookies in between two Url's in asp.net

Trying to get authentication cookie(s) using HttpWebRequest