Anonymous return in ASP.Net WebService

Question

I created a webservice function which returns an object (anonymous linq result)

 [WebMethod]
 [ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Json)]
 public object GetUser()
 {
 List<string> users = new List<string>
 {
 "Nora Aunor",
 "Pilita Corrales"
 };
 var result = users.Select(u => new
 {
 Name = u,
 Birthdate = DateTime.Now
 })
 .ToList();
 var retVal = new
 {
 Data = result,
 Count = result.Count
 };
 return retVal;
 }

if i use Fiddler to get the response, it returns ok with what data i expected

enter image description here

but if i use the browser, it just return an error

System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: <>f__AnonymousType2`2[System.Collections.Generic.List`1[<>f__AnonymousType1`2[System.String,System.DateTime]],System.Int32] cannot be serialized because it does not have a parameterless constructor.
 at System.Xml.Serialization.TypeDesc.CheckSupported()
 at System.Xml.Serialization.TypeScope.GetTypeDesc(Type type, MemberInfo source, Boolean directReference, Boolean throwOnError)
 at System.Xml.Serialization.XmlSerializationWriter.CreateUnknownTypeException(Type type)
 at System.Xml.Serialization.XmlSerializationWriter.WriteTypedPrimitive(String name, String ns, Object o, Boolean xsiType)
 at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write1_Object(String n, String ns, Object o, Boolean isNullable, Boolean needType)
 at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriter1.Write3_anyType(Object o)
 at Microsoft.Xml.Serialization.GeneratedAssembly.ObjectSerializer1.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()

Question: how to show the structure + data of the anonymous method into json that will show in the browser like this

{
 "d": {
 "Data": [{
 "Name": "Nora Aunor",
 "Birthdate": "\/Date(1393578983512)\/"
 },
 {
 "Name": "Pilita Corrales",
 "Birthdate": "\/Date(1393578983512)\/"
 }],
 "Count": 2
 }
}

or the default XML result.

Thanks in advance

• sloth: possible duplicate of Returning an anonymous type from MVC 4 Web Api fails with a serialization error
• Brian Rogers: @DominicKexel I don't think this is a duplicate of the question you linked. The OP is using older ASMX web services, not MVC or Web API.

Answer 1

Error is a Content-Type header. Try to remove it from request in Fiddler and you'll see same exception. Browser doesn't send Content-Type: application/json it and your webserice tries to return XML serialized object and fails. This is generally ASP.NET security policy. Check this url for more information