Question

我正在使用WebClient类将一些数据发布到网络表单。我想获取表单提交的响应状态代码。到目前为止，我已经找到了如果有异常

如何获取状态代码

Catch wex As WebException
        If TypeOf wex.Response Is HttpWebResponse Then
          msgbox(DirectCast(wex.Response, HttpWebResponse).StatusCode)
            End If

但是如果表单成功提交并且没有抛出异常，那么我将不知道状态代码（200,301,302，...）

当没有抛出异常时，有没有办法获取状态代码？

PS：我不想使用httpwebrequest / httpwebresponse

Answer 1

您可以检查错误是否为WebException类型，然后检查响应代码;

if (e.Error.GetType().Name == "WebException")
{
   WebException we = (WebException)e.Error;
   HttpWebResponse response = (System.Net.HttpWebResponse)we.Response;
   if (response.StatusCode==HttpStatusCode.NotFound)
      System.Diagnostics.Debug.WriteLine("Not found!");
}

或

try
{
    // send request
}
catch (WebException e)
{
    // check e.Status as above etc..
}

Answer 2

有一种方法可以使用反射来实现。它适用于.NET 4.0。它访问私有字段，如果不进行修改，可能无法在其他版本的.NET中使用。

我不知道为什么微软没有用属性公开这个字段。

private static int GetStatusCode(WebClient client, out string statusDescription)
{
    FieldInfo responseField = client.GetType().GetField("m_WebResponse", BindingFlags.Instance | BindingFlags.NonPublic);

    if (responseField != null)
    {
        HttpWebResponse response = responseField.GetValue(client) as HttpWebResponse;

        if (response != null)
        {
            statusDescription = response.StatusDescription;
            return (int)response.StatusCode;
        }
    }

    statusDescription = null;
    return 0;
}

Answer 3

如果您使用的是.Net 4.0（或更低版本）：

class BetterWebClient : WebClient
{
        private WebRequest _Request = null;

        protected override WebRequest GetWebRequest(Uri address)
        {
            this._Request = base.GetWebRequest(address);

            if (this._Request is HttpWebRequest)
            {
                ((HttpWebRequest)this._Request).AllowAutoRedirect = false;
            }

            return this._Request;
        } 

        public HttpStatusCode StatusCode()
        {
            HttpStatusCode result;

            if (this._Request == null)
            {
                throw (new InvalidOperationException("Unable to retrieve the status 
                       code, maybe you haven't made a request yet."));
            }

            HttpWebResponse response = base.GetWebResponse(this._Request) 
                                       as HttpWebResponse;

            if (response != null)
            {
                result = response.StatusCode;
            }
            else
            {
                throw (new InvalidOperationException("Unable to retrieve the status 
                       code, maybe you haven't made a request yet."));
            }

            return result;
        }
    }

如果您使用的是.Net 4.5.X或更高版本，请切换到HttpClient：

var response = await client.GetAsync("http://www.contoso.com/");
var statusCode = response.StatusCode;

Answer 4

试了一下。 ResponseHeaders不包含状态代码。

如果我没有弄错的话，WebClient能够在单个方法调用中抽象出多个不同的请求（例如正确处理100个继续响应，重定向等）。我怀疑在不使用HttpWebRequest和HttpWebResponse的情况下，可能无法使用不同的状态代码。

在我看来，如果您对中间状态代码不感兴趣，您可以放心地假设最终状态代码在2xx（成功）范围内，否则，呼叫将不会成功。

遗憾的是，状态代码不存在于ResponseHeaders字典中。

Answer 5

Erik的答案在Windows Phone上不起作用。以下是：

class WebClientEx : WebClient
{
    private WebResponse m_Resp = null;

    protected override WebResponse GetWebResponse(WebRequest Req, IAsyncResult ar)
    {
        try
        {
            this.m_Resp = base.GetWebResponse(request);
        }
        catch (WebException ex)
        {
            if (this.m_Resp == null)
                this.m_Resp = ex.Response;
        }
        return this.m_Resp;
    }

    public HttpStatusCode StatusCode
    {
        get
        {
            if (m_Resp != null && m_Resp is HttpWebResponse)
                return (m_Resp as HttpWebResponse).StatusCode;
            else
                return HttpStatusCode.OK;
        }
    }
}

至少在使用OpenReadAsync时会这样做;对于其他xxxAsync方法，强烈建议进行仔细测试。框架在代码路径的某个地方调用GetWebResponse;所有需要做的就是捕获并缓存响应对象。

此代码段中的回退代码为200，因为正确的HTTP错误 - 500,404等 - 无论如何都会被报告为异常。这个技巧的目的是捕获非错误代码，在我的特定情况下304（未修改）。所以后备假设如果状态代码在某种程度上不可用，至少它是一个非错误的。

Answer 6

你应该使用

if (e.Status == WebExceptionStatus.ProtocolError)
{
   HttpWebResponse response = (HttpWebResponse)ex.Response;             
   if (response.StatusCode == HttpStatusCode.NotFound)
      System.Diagnostics.Debug.WriteLine("Not found!");
}

Answer 7

以防其他人需要上述黑客的F＃版本。

open System
open System.IO
open System.Net

type WebClientEx() =
     inherit WebClient ()
     [<DefaultValue>] val mutable m_Resp : WebResponse

     override x.GetWebResponse (req: WebRequest ) =
        x.m_Resp <- base.GetWebResponse(req)
        (req :?> HttpWebRequest).AllowAutoRedirect <- false;
        x.m_Resp

     override x.GetWebResponse (req: WebRequest , ar: IAsyncResult  ) =
        x.m_Resp <- base.GetWebResponse(req, ar)
        (req :?> HttpWebRequest).AllowAutoRedirect <- false;
        x.m_Resp

     member x.StatusCode with get() : HttpStatusCode = 
            if not (obj.ReferenceEquals (x.m_Resp, null)) && x.m_Resp.GetType() = typeof<HttpWebResponse> then
                (x.m_Resp :?> HttpWebResponse).StatusCode
            else
                HttpStatusCode.OK

let wc = new WebClientEx()
let st = wc.OpenRead("http://www.stackoverflow.com")
let sr = new StreamReader(st)
let res = sr.ReadToEnd()
wc.StatusCode
sr.Close()
st.Close()

Answer 8

这是我用于扩展WebClient功能的内容。 StatusCode和StatusDescription将始终包含最新的响应代码/说明。

                /// <summary>
                /// An expanded web client that allows certificate auth and 
                /// the retrieval of status' for successful requests
                /// </summary>
                public class WebClientCert : WebClient
                {
                    private X509Certificate2 _cert;
                    public WebClientCert(X509Certificate2 cert) : base() { _cert = cert; }
                    protected override WebRequest GetWebRequest(Uri address)
                    {
                        HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
                        if (_cert != null) { request.ClientCertificates.Add(_cert); }
                        return request;
                    }
                    protected override WebResponse GetWebResponse(WebRequest request)
                    {
                        WebResponse response = null;
                        response = base.GetWebResponse(request);
                        HttpWebResponse baseResponse = response as HttpWebResponse;
                        StatusCode = baseResponse.StatusCode;
                        StatusDescription = baseResponse.StatusDescription;
                        return response;
                    }
                    /// <summary>
                    /// The most recent response statusCode
                    /// </summary>
                    public HttpStatusCode StatusCode { get; set; }
                    /// <summary>
                    /// The most recent response statusDescription
                    /// </summary>
                    public string StatusDescription { get; set; }
                }

因此，您可以通过以下方式发布帖子并获得结果：

            byte[] response = null;
            using (WebClientCert client = new WebClientCert())
            {
                response = client.UploadValues(postUri, PostFields);
                HttpStatusCode code = client.StatusCode;
                string description = client.StatusDescription;
                //Use this information
            }

Answer 9

您应该可以使用“client.ResponseHeaders [..]”调用，请参阅此link以获取从回复中获取内容的示例

Answer 10

您可以尝试使用此代码从WebException或OpenReadCompletedEventArgs.Error获取HTTP状态代码。它也适用于Silverlight，因为SL没有定义WebExceptionStatus.ProtocolError。

HttpStatusCode GetHttpStatusCode(System.Exception err)
{
    if (err is WebException)
    {
        WebException we = (WebException)err;
        if (we.Response is HttpWebResponse)
        {
            HttpWebResponse response = (HttpWebResponse)we.Response;
            return response.StatusCode;
        }
    }
    return 0;
}

如何从webclient获取状态代码？

10 个答案: