调用Web服务时，{“远程服务器返回错误：（500）内部服务器错误。”}

Question

我试图在运行时绑定到Web服务，并调用一个简单的方法来使此代码正常工作，并在尝试从Web服务获取答复时收到上述错误消息。 以下是以下代码，首先是我如何调用服务：

    Public Sub BeginInvoke(invokeCompleted As AsyncCallback)
    Dim invoke As New DelegateInvokeService(AddressOf Me.InvokeWebService)

    Dim result As IAsyncResult = invoke.BeginInvoke(invokeCompleted, Nothing)
End Sub

Public Function EndInvoke(result As IAsyncResult) As String
    Dim asyncResult = DirectCast(result, AsyncResult)
    Dim message As ReturnMessage = DirectCast(asyncResult.GetReplyMessage(), ReturnMessage)

    Return message.ReturnValue.ToString()
End Function

Public Function InvokeWebService() As String
    Try
        'Create the request
        Dim request As HttpWebRequest = CreateWebRequest()

        'write the soap envelope to request stream
        Using s As Stream = request.GetRequestStream()
            Using writer As New StreamWriter(s)
                writer.Write(CreateSoapEnvelope())
            End Using
        End Using

        'get the response from the web service
        Dim response As WebResponse = request.GetResponse()

        Dim stream As Stream = response.GetResponseStream()

        Dim reader As New StreamReader(stream)

        Dim str = reader.ReadToEnd()

        Return StripResponse(HttpUtility.HtmlDecode(str))
    Catch ex As Exception
        Return ex.Message
    End Try
End Function

现在用于构建肥皂包和Web请求：

Private Function CreateSoapEnvelope() As String
    Dim method As String = "<" & WebMethod & " xmlns=""http://tempuri.org/"">"
    Dim params As String = Parameters.Aggregate(String.Empty, Function(current, param) current & "<" & param.Name & ">" & param.Value & "</" & param.Name & ">")

    method &= params & "</" & WebMethod & ">"

    Dim sb As New StringBuilder(SoapEnvelope)
    sb.Insert(sb.ToString().IndexOf("</soap:Body>"), method)

    Return sb.ToString()
End Function

Private Function CreateWebRequest() As HttpWebRequest
    Dim request As HttpWebRequest = DirectCast(WebRequest.Create(Url), HttpWebRequest)
    If WSServiceType = ServiceType.WCF Then
        request.Headers.Add("SOAPAction", """http://tempuri.org/" & WCFContractName & "/" & WebMethod & """")
    Else
        request.Headers.Add("SOAPAction", """http://tempuri.org/" & WebMethod & """")
    End If

    request.Headers.Add("To", Url)

    request.ContentType = "text/xml;charset=""utf-8"""
    request.Accept = "text/xml"
    request.Method = "POST"
    Return request
End Function

SoapEnvelope变量如下所示：

Private Const SoapEnvelope As String = "<soap:Envelope " & _
    "xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' " & _
    "xmlns:xsd='http://www.w3.org/2001/XMLSchema' " & _
    "xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'>" & _
    "<soap:Body></soap:Body></soap:Envelope>"

这就是我调用上述调用的方式：

Protected Sub GoButtonClick(sender As Object, e As EventArgs) Handles GoButton.Click
    _oClient = New SoapClient()

    Dim params As New List(Of SoapClient.Parameter)
    params.Add(New SoapClient.Parameter() With {.Name = "str", .Value = "Richard"})

    With _oClient
        .Url = "http://localhost:7659/WebServices/SampleService.asmx"
        .WebMethod = "HelloWorld"
        .WSServiceType = SoapClient.ServiceType.Traditional
        .Parameters = params
    End With

    _oClient.BeginInvoke(AddressOf InvokeCompleted)
End Sub

Public Sub InvokeCompleted(result As IAsyncResult)
    ErrorMessage.Text = _oClient.EndInvoke(result)
End Sub

错误在InvokeWebService的这一行上生成

'get the response from the web service
Dim response As WebResponse = request.GetResponse()

有人知道我在哪里错吗？

Answer 1

事实证明，这是我正在测试的示例Web服务的问题，一旦修复了该错误，以上代码就可以正常工作。