jquery ajax call return JSON parsing error

Question

I am using jquery to call an ajax wcf method that returns a list of objects as a JSON string. The JSON string looks like this when inspecting it in fiddler2 (in TextView):

Answer 1

I assume you want to return the value of ser.Serialize(query.ToArray()) to the client (an array). But you're returning it as a string, so WCF will escape that JSON into a string, and what you'll end up is not an array, but a string.

Since you're using anonymous types, which aren't natively supported by WCF, you need to use the JavaScriptSerializer. So to prevent the double-encoding of the JSON (into the string) you should return the data as a Stream instead, so that WCF won't touch your data (see sample code below).

One more thing: I see your response has a {"d":...} wrapper, which suggests that you're using the / WebScriptEnablingBehavior / WebScriptServiceHostFactory when defining your service / endpoint. Since you're not using the ASP.NET AJAX library, you don't need that wrapping, so you can use the "simpler" / WebHttpBehavior / WebServiceHostFactory instead, and your response won't be wrapped in that "d" object.

[OperationContract]
[WebGet(ResponseFormat = WebMessageFormat.Json)]
public System.IO.Stream GetPeople(Guid groupId)
{
    using (SchedulerContext context = new SchedulerContext())
    {
        JavaScriptSerializer ser = new JavaScriptSerializer();

        var query = from p in context.People
                    where p.Group_ID == groupId
                    select new
                    {
                        p.ID,
                        p.Name,
                        p.Surname
                    };

        string json = ser.Serialize(query.ToArray());
        using (MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json)))
        {
            WebOperationContext.Current.OutgoingResponse.ContentType = "application/json; charset=utf-8";
            return ms;
        }

}