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: &lt;&gt;f__AnonymousType2`2[System.Collections.Generic.List`1[&lt;&gt;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

possible duplicate of Returning an anonymous type from MVC 4 Web Api fails with a serialization error — sloth
– sloth, Commented Feb 28, 2014 at 10:46
@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. — Brian Rogers
– Brian Rogers, Commented Feb 28, 2014 at 16:39

Sergio · Accepted Answer · 2014-02-28 10:53:46Z

2

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

answered Feb 28, 2014 at 10:53

Sergio

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