要弄清楚重定向URL的方式 [英] A way to figure out redirection URL

问题描述

由于它被重定向到一个第三方网站B中的URL的，在我的应用我需要找出网址B.指定网址A和DB插入，这可能是一个Windows应用程序或网页或其他任何方式速度更快，使用C＃更轻松！
谢谢！

Given a URL A which gets redirected to a 3rd party website B, in my application I need to to find out URL B for the given url A and insert it in DB , this can be a windows application or web or whichever way is faster and easier using C#! Thanks !

P.S。我不要求的代码数据库中插入。

P.S. I do not require the code to insert in DB.

推荐答案

WebRequest的如下的重定向，无需用户干预，因此，如果重定向使用301 / 302状态码，然后下面的工作。

WebRequest follows redirects without user intervention, so if the redirects are using 301/302 status codes then the following will work

WebRequest request = WebRequest.Create(destination);
WebResponse response = request.GetResponse();
Console.WriteLine(response.ResponseUri);

如果是使用JavaScript创建重定向或HTTP-EQUIV meta标签，那么你正在做的有来解析页面，寻找那些。该HTML敏捷包可能是做到这一点的最好办法。

If the redirects are created using javascript or HTTP-Equiv meta tags then you're doing to have to parse the page and look for those. The HTML agility pack is probably the best way to do this.

要借此远一点以下是将手工解决主HTTP重定向状态码的类，建立一个历史，因为它不用

To take this a little further the following is a class which will manually resolve the main HTTP redirect status codes, building up a history as it goes

/// <summary>
/// Digs through HTTP redirects until a non-redirected URL is found.
/// </summary>
public class Digger
{
    /// <summary>
    /// Initializes a new instance of the <see cref="Digger"/> class.
    /// </summary>
    public Digger() : this(20)
    {            
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="Digger"/> class.
    /// </summary>
    /// <param name="maximumDepth">The maximum depth of redirects to parse.</param>
    public Digger(int maximumDepth)
    {
        this.MaximumDepth = maximumDepth;
    }

    /// <summary>
    /// Gets the maximum depth of redirects to parse.
    /// </summary>
    /// <value>The maximum depth of redirects to parse.</value>
    public int MaximumDepth
    {
        get; 
        private set;
    }

    /// <summary>
    /// Resolves any redirects at the specified URI.
    /// </summary>
    /// <param name="destination">The initial URI.</param>
    /// <returns>The URI after resolving any HTTP redirects.</returns>
    public Uri Resolve(Uri destination)
    {
        List<Uri> redirectHistory = new List<Uri>();
        return this.Resolve(destination, redirectHistory);
    }

    /// <summary>
    /// Resolves any redirects at the specified URI.
    /// </summary>
    /// <param name="destination">The initial URI.</param>
    /// <param name="redirectHistory">A collection of <see cref="Uri"/> objects representing the redirect history.</param>
    /// <returns>The URI after resolving any HTTP redirects.</returns>
    public Uri Resolve(Uri destination, ICollection<Uri> redirectHistory)
    {
        redirectHistory.Add(destination);
        return this.Resolve(destination, this.MaximumDepth, redirectHistory);
    }

    /// <summary>
    /// Resolves any redirects at the specified URI.
    /// </summary>
    /// <param name="destination">The initial URI.</param>
    /// <param name="hopsLeft">The maximum number of redirects left to follow.</param>
    /// <param name="redirectHistory">A collection of <see cref="Uri"/> objects representing the redirect history.</param>
    /// <returns>The URI after resolving any HTTP redirects.</returns>
    private Uri Resolve(Uri destination, int hopsLeft, ICollection<Uri> redirectHistory)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(destination);
        request.AllowAutoRedirect = false;
        request.Method = "HEAD";

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();

        Uri resolvedUri;

        if (response.StatusCode == HttpStatusCode.Redirect || 
            response.StatusCode == HttpStatusCode.Moved || 
            response.StatusCode == HttpStatusCode.MovedPermanently)
        {
            if (hopsLeft > 0)
            {
                Uri redirectUri = new Uri(response.GetResponseHeader("Location"));
                if (redirectHistory.Contains(redirectUri))
                {
                    throw new Exception("Recursive redirection found");
                }

                redirectHistory.Add(redirectUri);
                resolvedUri = this.Resolve(redirectUri, hopsLeft - 1, redirectHistory);
            }
            else
            {
                throw new Exception("Maximum redirect depth reached");
            }
        }
        else
        {
            resolvedUri = response.ResponseUri;
        }

        return resolvedUri;            
    }
}

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