为什么我的HttpWebRequest返回400 Bad请求？

Question

以下代码失败,出现400错误请求异常.我的网络连接很好,我可以去网站,但我不能用HttpWebRequest得到这个uri.

private void button3_Click(object sender, EventArgs e)
{
    WebRequest req = HttpWebRequest.Create(@"http://www.youtube.com/");
    try
    {
        //returns a 400 bad request... Any ideas???
        WebResponse response = req.GetResponse();
    }
    catch (WebException ex)
    {
        Log(ex.Message);                
    }
}

Answer 1

首先,将WebRequest转换为HttpWebRequest,如下所示:

HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(@"http://www.youtube.com/");

然后,添加以下代码行:

req.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

Answer 2

在HttpWebRequest中设置UserAgent和Referer:

var request = (HttpWebRequest)WebRequest.Create(@"http://www.youtube.com/");
request.Referer = "http://www.youtube.com/"; // optional
request.UserAgent =
    "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; WOW64; " +
    "Trident/4.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; " +
    ".NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618; " +
    "InfoPath.2; OfficeLiveConnector.1.3; OfficeLivePatch.0.0)";
try
{
    var response = (HttpWebResponse)request.GetResponse();
    using (var reader = new StreamReader(response.GetResponseStream()))
    {
        var html = reader.ReadToEnd();
    }
}
catch (WebException ex)
{
    Log(ex);
}