Question

在.NET中检查Web服务器回复GET请求的状态代码的最简单方法是什么？

请注意，我不需要响应的正文。实际上，如果可能的话，只应该请求标题。然而，话虽如此，如果要求省略响应的主体会显着增加代码的复杂性，接收正文就可以了。

另外，我特别感兴趣的是捕获所有可能的适当的异常（System.Net.WebException，System.IO.IOException，System.Net.Sockets.SocketException等），这个例程每天会运行数千次。

Answer 1

public HttpStatusCode GetHeaders(string url)
    {
        HttpStatusCode result = default(HttpStatusCode);

        var request = HttpWebRequest.Create(url);
        request.Method = "HEAD";
        using (var response = request.GetResponse() as HttpWebResponse)
        {
            if (response != null)
            {
                result = response.StatusCode;
                response.Close();
            }
        }

        return result;
    }

Answer 2

使用HTTP方法HEAD，它与GET相同，但不返回正文：

var request = (HttpWebRequest)WebRequest.Create("http://www.example.com");
request.Method = "HEAD";
var response = (HttpWebResponse)request.GetResponse();

// status code...
response.StatusCode;

来自Section 9.4 of RFC2616：

HEAD方法与GET相同除了服务器不能返回响应中的消息正文。该 HTTP中包含的元信息响应HEAD请求的标头应该与信息完全相同发送以响应GET请求。该方法可用于获得关于实体的元信息没有提出要求所暗示的转移实体 - 身体本身。此方法通常用于测试有效性的超文本链接，可访问性，最近修改

Answer 3

我最终采用了这种方法，结合了IvanFerić的答案和适当的特殊案例支持：

public async Task<bool> IsAccessibleAsync (string url)
{
    if (url == null)
        throw new ArgumentNullException ("url");

    if (url.IndexOf (':') < 0)
        url = "http://" + url.TrimStart ('/');

    if (!Uri.IsWellFormedUriString (url, UriKind.Absolute))
        return false;

    var request = (HttpWebRequest) WebRequest.Create (url);
    request.Method = "HEAD";

    try
    {
        using (var response = await request.GetResponseAsync () as HttpWebResponse)
        {
            if (response != null && response.StatusCode == HttpStatusCode.OK)
                return true;

            return false;
        }
    }
    catch (WebException)
    {
        return false;
    }
}

Answer 4

如果你使用HttpWebRequest，那很简单：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://url");
request.Method = "GET";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
HttpStatusCode status = response.StatusCode;

您可以使用全局catch子句包围它，或查看WebRequest.Create和.GetResponse的文档以查看将抛出的异常。

Answer 5

这是我想出的处理404异常的方法。下面还有一个测试。

public static HttpStatusCode GetUrlStatus(string url, string userAgent)
{
    HttpStatusCode result = default(HttpStatusCode);

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.UserAgent = userAgent;
    request.Method = "HEAD";

    try
    {
        using (var response = request.GetResponse() as HttpWebResponse)
        {
            if (response != null)
            {
                result = response.StatusCode;
                response.Close();
            }
        }
    }
    catch (WebException we)
    {
        result = ((HttpWebResponse)we.Response).StatusCode;
    }

    return result;
}


[Test]
public void PageNotFoundShouldReturn404()
{
    //Arrange
    HttpStatusCode expected = HttpStatusCode.NotFound;
    string userAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36";

    //Act
    HttpStatusCode result = WebHelper.GetUrlStatus("http://www.kellermansoftware.com/SomePageThatDoesNotExist", userAgent);

    //Assert
    Assert.AreEqual(expected, result);
}

.NET：检查URL响应状态代码？

5 个答案: