当状态不是200时,如何从Web请求中读取响应？

Question

当我收到Web异常时,我很难从vb.net中的HTTP Web请求获取响应文本.

这是我正在做的代码.

Try
            myWebResponse = CType(request.GetResponse(), HttpWebResponse)
            myStreamReader = New StreamReader(myWebResponse.GetResponseStream())

            ResponseText = myStreamReader.ReadToEnd
            If myWebResponse.StatusCode = HttpStatusCode.Accepted Or myWebResponse.StatusCode = 200 Then
                SendResult = True 'Sent 
                SendStatus = 1 'message sent successfully
                Try
                    Integer.TryParse(myWebResponse.Headers("Number-Of-MT-PDU"), num_MT_PDU)
                Catch ex As Exception
                End Try
            Else
                SendStatus = 2 'message processed but not sent successfully
            End If
        Catch e As WebException
            If (e.Status = WebExceptionStatus.ProtocolError) Then
                Dim response As WebResponse = e.Response
                Using (response)
                    Dim httpResponse As HttpWebResponse = CType(response, HttpWebResponse)
                    statusCode = httpResponse.StatusCode
                    Try
                        myStreamReader = New StreamReader(response.GetResponseStream())
                        Using (myStreamReader)
                            ResponseText = myStreamReader.ReadToEnd & "Status Description = " & HttpWebResponse.StatusDescription
                        End Using
                    Catch ex As Exception
                        Logger.LogError(Me, ex)
                    End Try
                End Using

令人讨厌的是,我正在联系的API使用404作为有效响应.如果我将请求放在浏览器中,将显示一些消息文本.我希望能够在我的程序中使用该文本.我不能简单地使用错误代码来确定操作,因为我认为我无法区分有效的404响应和实际错误.

在这行代码中

myWebResponse = CType(request.GetResponse(), HttpWebResponse)

抛出一个例外.

在例外情况下,我可以获得404代码和描述,但不能获得响应流.它始终为空.

如果我得到200响应,我得到响应流中的文本没问题.

在Web异常响应对象(在Visual Studios调试器中),我检查了标头和对象值,无法在任何地方找到响应文本.如果我在浏览器中粘贴请求URL,即使它是404,我也会得到响应文本.

小提琴手的原始回应:

HTTP/1.1 404 Not Found Connection: close Content-Type: text/plain; charset=UTF-8 Content-Length: 35 "The response Message"

关于如何在我的程序中获得"响应消息"的任何想法？我必须在服务器上使用.Net.

感谢任何人都能给予的任何帮助.

Answer 1

此 LINQPad 查询工作正常，转储我的 Web 服务器的“未找到”错误网页提供的 HTML：

Dim rq = System.Net.WebRequest.Create(New Uri("http://localhost/test"))
Try 
  Dim rs = rq.GetResponse
  rs.Dump
Catch Ex As System.Net.WebException
 Dim rs = Ex.Response
 Call (New StreamReader(rs.GetResponseStream)).ReadToEnd.Dump
End Try

仅供参考，您的代码对我有用，除了假定的打字错误HttpWebResponse.StatusDescription（并注释掉“不相关的东西”），再次作为 LINQPad 查询（在 .NET 4.0 中）：

Dim request = WebRequest.Create("http://localhost/test")
Dim myStreamReader As StreamReader
Dim SendStatus As Integer = -1
Dim statusCode As HttpStatusCode
Dim ResponseText As String
Try
    Dim myWebResponse = CType(request.GetResponse(), HttpWebResponse)
        myStreamReader = New StreamReader(myWebResponse.GetResponseStream())

        ResponseText = myStreamReader.ReadToEnd
        If myWebResponse.StatusCode = HttpStatusCode.Accepted Or myWebResponse.StatusCode = 200 Then
            'SendResult = True 'Sent 
            SendStatus = 1 'message sent successfully
            'Try
            '    Integer.TryParse(myWebResponse.Headers("Number-Of-MT-PDU"), num_MT_PDU)
            'Catch ex As Exception
            'End Try
        Else
            SendStatus = 2 'message processed but not sent successfully
        End If
    Catch e As WebException
        If (e.Status = WebExceptionStatus.ProtocolError) Then
            Dim response As WebResponse = e.Response
            Using (response)
                Dim httpResponse As HttpWebResponse = CType(response, HttpWebResponse)
                statusCode = httpResponse.StatusCode
                Try
                    myStreamReader = New StreamReader(response.GetResponseStream())
                    Using (myStreamReader)
                        ResponseText = myStreamReader.ReadToEnd & "Status Description = " & httpResponse.StatusDescription ' HttpWebResponse.StatusDescription
                    End Using
                Catch ex As Exception
                    'Logger.LogError(Me, ex)
                    ex.Dump("Exception")
                End Try
            End Using
      End If
End Try
ResponseText.Dump("ResponseText")

我还确认了上述代码（As添加了推断子句并将调用转换.Dump为Console.WriteLine）可以在 .NET 2.0 和 VB8 中工作。