How to return JSON in a Webservice?

Question

I need a Hello World example...

[WebService(Namespace = "xxxxx")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ScriptService()]
public class Something : System.Web.Services.WebService
{
    public Something() { }

    [WebMethod]
    [ScriptMethod(ResponseFormat=ResponseFormat.Json)]
    public string HelloWorld()
    {
        return "{Message:'hello world'}";
    }
}

Because it generates an error

{"Message":"Invalid JSON primitive: value.","StackTrace":"   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializePrimitiveObject()\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer)\r\n   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit)\r\n   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input)\r\n   at System.Web.Script.Services.RestHandler.GetRawParamsFromPostRequest(HttpContext context, JavaScriptSerializer serializer)\r\n   at System.Web.Script.Services.RestHandler.GetRawParams(WebServiceMethodData methodData, HttpContext context)\r\n   at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.ArgumentException"}

What's wrong?

Edit: And what if I need to return {Message:'',Type:1} ?

Edit2: The answer for the last one is: I can return a Dictionary<string, string>

Answer 1

You only need to return a normal (that is, non-JSON) String from your function like:

 return "Hello World"

Assuming you are using .Net 3.5, your JSON response will be:

 {"d":"Hello World"}

Answer 2

Well, if you need your JSON to be exactelly in the {Message:Hello wolrd} pair (or if you plan to use your webservice for anything more complex) you will probably need to create a serializable class for that

[Serializable]
class MessageClass
{
    public string Message {get;set;}

    //any public member will automatically  be serialized  as JSON
    punlic bool WillAlsoBeJsoned {get;set;}

    //unless explicitly told not to
    [NonSerialized] 
    [ScriptIgnoreAttribute]
    public string WillNotBeJsoned {get;set;}
}

then in your webservice

     //{Message :"Hello World",WillAlsoBeJsoned :false}
    [WebMethod] 
    public string HelloWorld() 


       { 
             var returnObject = new MessageClass();
             returnObject.Message= "Hello World";
             var oSerializer = new System.Web.Script.Serialization.JavaScriptSerializer();        
            return  oSerializer.Serialize(returnObject);
} 

    // return an array of the same items
    //[{Message :"Hello World",WillAlsoBeJsoned :false},
    //{Message :"something else",WillAlsoBeJsoned :false}]
    [WebMethod] 

        public string HelloWorldList() 
        { 
             var returnObject = new List<MessageClass>();

             var message1= new MessageClass();       
             message1.Message= "Hello World";

             var message2= new MessageClass();
             message2.Message= "something else";

             returnObject.Add(message1);
             returnObject.Add(message2);

             var oSerializer = new System.Web.Script.Serialization.JavaScriptSerializer();        
            return  oSerializer.Serialize(returnObject);

}