ASMX 服务错误 - 使用 XmlInclude 或 SoapInclude 属性指定静态未知的类型

Question

I have an Asmx service with a web method. Within that web method i am calling a rest endpoint (Logic app endpoint). The logic app rest endpoint accepts the request and returns a success 200 response.

  using (var client = new HttpClient())
            {
                client.BaseAddress = new Uri("base address");
                var content = new StringContent(JsonConvert.SerializeObject(request, Formatting.Indented), Encoding.UTF8, "application/json");
                var result = await client.PostAsync("some-uri", content);                  
            }

As soon as i hit the client.postasync line i get the following error:

System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: The type System.Threading.Tasks.Task`1[[System.Threading.Tasks.VoidTaskResult, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically.
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write2_Task(String n, String ns, Task o, Boolean isNullable, Boolean needType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write3_Task(Object o)
   at Microsoft.Xml.Serialization.GeneratedAssembly.TaskSerializer.Serialize(Object objectToSerialize, XmlSerializationWriter writer)
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id)
   --- End of inner exception stack trace ---
   at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id)
   at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces)
   at System.Web.Services.Protocols.XmlReturnWriter.Write(HttpResponse response, Stream outputStream, Object returnValue)
   at System.Web.Services.Protocols.HttpServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream)
   at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues)
   at System.Web.Services.Protocols.WebServiceHandler.Invoke()

Answer 1

I found the error. The webmethod was made async and that caused this issue. I made the web method to return void and changed the http client post request line of code to the following:

  var result = client.PostAsync(reqUri, requestContent).GetAwaiter().GetResult();