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码。到目前为止，我已经找到了如果出现异常如何获取状态码
Catch wex As WebException
If TypeOf wex.Response Is HttpWebResponse Then
msgbox(DirectCast(wex.Response, HttpWebResponse).StatusCode)
End If
但是如果表单提交成功并且没有抛出异常，那么我将不知道状态码（200,301,302，...）
在没有抛出异常的情况下，有没有办法获取状态码？
PS：我不喜欢使用httpwebrequest/httpwebresponse
【问题讨论】：
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..
}
【讨论】：
有一种使用反射的方法。它适用于 .NET 4.0。它访问一个私有字段，未经修改可能无法在其他版本的 .NET 中工作。
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;
}
【讨论】：
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;
【讨论】：
试过了。 ResponseHeaders 不包含状态码。
如果我没记错的话，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）。我怀疑如果不使用HttpWebRequest 和HttpWebResponse，可能无法使用不同的状态码。
我突然想到，如果您对中间状态码不感兴趣，您可以放心地假设最终状态码在 2xx（成功）范围内，否则调用不会成功。
很遗憾，ResponseHeaders 字典中没有状态码。
【讨论】：
Erik 的回答无法在 Windows Phone 上按原样运行。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时是这样；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处调用 GetWebResponse；只需捕获并缓存响应对象即可。
此 sn-p 中的后备代码为 200，因为真正的 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，在我的特定情况下为 304（未修改）。所以回退假设如果状态码不可用，至少它是一个非错误的。
【讨论】：
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!");
}
【讨论】：
However if the form is submitted successfully and no exception is thrown...
这是我用来扩展 WebClient 功能的。 StatusCode 和 StatusDescription 将始终包含最新的响应代码/描述。
/// <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
}
【讨论】：
以防万一其他人需要上述 hack 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()
【讨论】：
您应该能够使用“client.ResponseHeaders[..]”调用，请参阅link，了解从响应中取回内容的示例
【讨论】：
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;
}
【讨论】：