.NET Core 中 WebRequest 的重定向

Question

我使用 .NET 4.7.1 在 C# 中编写了以下程序：

var req = (HttpWebRequest) WebRequest.Create(myUrl);
req.AllowAutoRedirect = false;
var rsp = req.GetResponse();
Console.WriteLine(rsp.Headers["Location"]);

我请求的网站正在返回 301 响应，并且“位置”header 包含要重定向到的 URL。

如果我使用 .NET Core 2.1 做完全相同的事情，我会从对 GetResponse 的调用中抛出一个 WebException。我怎样才能避免这种情况？

Answer 1

基于this，您需要将其捕获在try/catch块中并检查WebException:

If you set AllowAutoRedirect, then you will end up not following the redirect. That means ending up with the 301 response. HttpWebRequest (unlike HttpClient) throws exceptions for non-successful (non-200) status codes. So, getting an exception (most likely a WebException) is expected. So, if you need to handle that redirect (which is HTTPS -> HTTP by the way), you need to trap it in try/catch block and inspect the WebException etc. That is standard use of HttpWebRequest.

That is why we recommend devs use HttpClient which has an easier use pattern.

像这样：

WebResponse rsp;

try 
{
   rsp = req.GetResponse();
}

catch(WebException ex) 
{
    if(ex.Message.Contains("301"))
        rsp = ex.Result;
}

Answer 2

我在处理它时几乎已经弄明白了，但我想我会 post 在这里以防其他人运行遇到同样的问题。

响应作为抛出的异常的一部分包含在内，因此我能够通过将我的代码修改为以下内容来获得与 .NET 4.7.1 中相同的行为：

var req = (HttpWebRequest) WebRequest.Create(myUrl);
req.AllowAutoRedirect = false;
try
{
    var rsp = req.GetResponse();
    Console.WriteLine(rsp.Headers["Location"]);
}
catch (WebException e)
{
    var rsp = (HttpWebResponse) e.Response;
    if (rsp.StatusCode == HttpStatusCode.Moved ||
        rsp.StatusCode == HttpStatusCode.MovedPermanently ||
        rsp.StatusCode == HttpStatusCode.Found)
    {
        Console.WriteLine(rsp.Headers["Location"]);
    }
    else throw;
}

.NET Core 中 WebRequest 的重定向

Redirect of WebRequest in .NET Core

c#

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.net-core

asp.net-core-2.0