c# - HttpWebRequest 错误：503 服务器不可用

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 状态码。但是，它还会返回响应正文以及 503 错误条件（打开该 URL 时在浏览器中看到的内容）。

您可以访问异常Response属性中的响应（如果有 503 响应，则引发的异常是 a WebException，它有一个Response属性）。您需要捕获此异常并正确处理

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;