c# - HttpWeb 请求错误 : 503 server unavailable

Question

我正在使用 HttpWebRequest，但在执行 GetResponse() 时出现错误。

我使用这段代码:

private void button1_Click(object sender, EventArgs e)
    {
        Uri myUri = new Uri("http://www.google.com/sorry/?continue=http://www.google.com/search%3Fq%3Dyamaha");
        // Create a 'HttpWebRequest' object for the specified url. 
        HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(myUri);
        // Set the user agent as if we were a web browser
        myHttpWebRequest.UserAgent = @"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4";

        HttpWebResponse myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
        var stream = myHttpWebResponse.GetResponseStream();
        var reader = new StreamReader(stream);
        var html = reader.ReadToEnd();
        // Release resources of response object.
        myHttpWebResponse.Close();

        textBox1.Text = html;
    }

Answer 1

服务器确实返回了 503 HTTP 状态代码。但是，它还会返回一个响应正文以及 503 错误条件(如果您打开该 URL，您会在浏览器中看到的内容)。

您可以访问异常的 Response 属性中的响应(如果有 503 响应，引发的异常是 WebException，它有一个 响应属性)。你需要捕获这个异常并妥善处理它

具体来说，您的代码可能如下所示:

string html;

try
{
    var myUri = new Uri("http://www.google.com/sorry/?continue=http://www.google.com/search%3Fq%3Dyamaha");
    // Create a 'HttpWebRequest' object for the specified url. 
    var myHttpWebRequest = (HttpWebRequest)WebRequest.Create(myUri);
    // Set the user agent as if we were a web browser
    myHttpWebRequest.UserAgent = @"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4";

    var myHttpWebResponse = (HttpWebResponse)myHttpWebRequest.GetResponse();
    var stream = myHttpWebResponse.GetResponseStream();
    var reader = new StreamReader(stream);
    html = reader.ReadToEnd();
    // Release resources of response object.
    myHttpWebResponse.Close();
}
catch (WebException ex)
{
    using(var sr = new StreamReader(ex.Response.GetResponseStream()))
        html = sr.ReadToEnd();
}

textBox1.Text = html;