Getting the location from a WebClient on a HTTP 30

问题:

I have a URL that returns a HTTP 302 redirect, and I would like to get the URL it redirects to.

The problem is that System.Net.WebClient seems to actually follow it, which is bad. HttpWebRequest seems to do the same.

Is there a way to make a simple HTTP Request and get back the target Location without the WebClient following it?

I'm tempted to do raw socket communication as HTTP is simple enough, but the site uses HTTPS and I don't want to do the Handshaking.

At the end, I don't care which class I use, I just don't want it to follow HTTP 302 Redirects :)

回答1:

On HttpWebRequest you can set AllowAutoRedirect to false to handle the redirect yourself.

回答2:

It's pretty easy to do

Let's assume you've created an HttpWebRequest called myRequest

// don't allow redirects, they are allowed by default so we're going to override
myRequest.AllowAutoRedirect = false;

// send the request
HttpWebResponse response = myRequest.GetResponse();

// check the header for a Location value
if( response.Headers["Location"] == null )
{
  // null means no redirect
}
else
{
  // anything non null means we got a redirect
}

Excuse any compile errors I don't have VS right in front of me, but I've used this in the past to check for redirects.

回答3:

The HttpWebRequest has a property AllowAutoRedirect which you can set to false (it is always true for WebClient), and then get the Location HTTP header.

回答4:

Also, for someone who just needs the new location, HttpResponseMessage has a RequestMessage property. Sometimes it can be useful, because WebClient doesn't support changing the AllowAutoRedirect property once it's been set.