从核心 API 调用 WCF 服务导致错误：缓冲 XML 内容所需的大小超出了缓冲区配额

Question

We have an existing WCF Webservice used in a web application and for a third party to supply data I have created an API in dotnet core to pass on that information.

When I run the API I see that I get to the desired function in the webservice. The return value of the function is an XML.

When the webservice returns the XML to the API I get an error in the API. I never get to see what the response is, it goes directly to an exception.

The error:

The size necessary to buffer the XML content exceeded the buffer quota

This is the API method that calls the a private method to call the webservice:

 private async Task<string?> GetSessionIdAsync()
{
  try
  {
    var serviceClient = GetWsClient();

    string sessionUser = _config["Wmws:sessionUserName"];
    string sessionPassword = _config["Wmws:sessionPassWord"];

    var result = await serviceClient.GetSessionIdAsync(sessionUser, sessionPassword);

    return "";
  }
  catch (Exception ex)
  {
    _logger.Log(LogLevel.Information, "Webservice error: {@fout}", $"{ex.Message}");
    return null;
  }
}

And the method that actually makes the connection:

 private W2DWebservice_WM.W2DWebserviceClient GetWsClient()
{
  string username = _config["Wmws:UNT_UserName"];
  string password = _config["Wmws:UNT_PassWord"];
  string serviceClientEndpoint = _config["Wmws:UNT_clientEndpoint"];
  int quotaSize = 2147483647;

  // binding instellen
  WSHttpBinding binding = new WSHttpBinding
  {
    Security = new WSHttpSecurity()
    {
      Mode = SecurityMode.TransportWithMessageCredential,
      Transport = new HttpTransportSecurity()
      {
        ClientCredentialType = HttpClientCredentialType.Certificate
      },
      Message = new NonDualMessageSecurityOverHttp()
      {
        ClientCredentialType = MessageCredentialType.UserName,
        EstablishSecurityContext = false,
        NegotiateServiceCredential = false
      }
    },
    TextEncoding = System.Text.Encoding.UTF8,
    ReaderQuotas = new System.Xml.XmlDictionaryReaderQuotas()
    {
      MaxDepth = quotaSize,
      MaxStringContentLength = quotaSize,
      MaxArrayLength = quotaSize,
      MaxBytesPerRead = quotaSize,
      MaxNameTableCharCount = quotaSize
    }, 
    MaxBufferPoolSize = quotaSize, 
    MaxReceivedMessageSize = quotaSize
  };

  // Nieuwe binding maken en MTOM toe te kunnen voegen
  var messageEncodingBindingElementType = typeof(MessageEncodingBindingElement);
  var elements = binding.CreateBindingElements();

  IEnumerable<BindingElement> elementsWithoutEncodingElement = elements.Where(item => !messageEncodingBindingElementType.IsAssignableFrom(item.GetType()));
  var existingEncodingElement = (MessageEncodingBindingElement)elements.Where(item => messageEncodingBindingElementType.IsAssignableFrom(item.GetType())).First();

  var newEncodingElement = new MtomMessageEncoderBindingElement(existingEncodingElement);

  var customBinding = new CustomBinding(elementsWithoutEncodingElement.Prepend(newEncodingElement));

  EndpointAddress address = new EndpointAddress(serviceClientEndpoint);

  // serviceClient maken
  var serviceClient = new W2DWebservice_WM.W2DWebserviceClient(customBinding, address);
  serviceClient.ClientCredentials.UserName.UserName = username;
  serviceClient.ClientCredentials.UserName.Password = password;
  
  if (IsDevelopment)
  {
    // dit zou niet nodig moeten zijn als het op de server staat
    serviceClient.ClientCredentials.ClientCertificate.SetCertificate(StoreLocation.LocalMachine, StoreName.My, X509FindType.FindByIssuerName, "TempCA");

    serviceClient.ClientCredentials.ServiceCertificate.SslCertificateAuthentication = new X509ServiceCertificateAuthentication
    {
      CertificateValidationMode = X509CertificateValidationMode.None,
      TrustedStoreLocation = StoreLocation.LocalMachine,
      RevocationMode = X509RevocationMode.NoCheck
    };
  }

  return serviceClient;
}

This is the method in the webservice (in vb.net):

 Public Function GetSessionId(username As String, password As String) As XmlDocument Implements IW2DWebservice.GetSessionId


   Dim xmldto As XmlDTO = Authorization("", "", "", "", username, password, "WEBSERVICE")


   Dim retXml As New XmlDocument
   retXml.LoadXml($"<sessionId>{xmldto.SessionID}</sessionId>")

   Return retXml
 End Function

The webservice is linked via connected services.

So like said when the webservice method returns to the API it goes straight to the catch.

Why is this happening?

What is returned from the webservice? Is it just the little XML or is it an entire soap message? How can I read that?

Any help is appreciated.

Answer 1

We figured out that the problem has to do with using Mtom for the messageEconding. We couldn't switch the wcf to Text in stead of Mtom because it is an existing service so we ended up with adding a second endpoint to the webservice which uses Text for textencoding.

I used the WcfCoreMtomEncoderV2 package but it didn't work.

So I didn't need to create the customBinding anymore. I just used the already created binding and changed the endpointaddress to the newly added endpoint on the webservice.