WCF and Anonymous Types - wcf

Question

I want to return an anonymous type over WCF. Is this possible?

Answer 1

You cannot use anonymous types, but maybe you are talking about WCF and untyped messages?
There is an option in WCF to just define a parameter of type Message (and possibly a return value of the same type). This is just the raw message that goes to WCF (and comes back from it).
I can't find much good information out there - there's some documentation on MSDN, but the best I've seen so far is Kurt Claeys' blog post WCF : Untyped messages on WCF operations.
I would not recommend using this approach - it's a lot more grunt work to handle the message contents directly yourself and that's what WCF is trying to spare us from - but if you absolutely, positively have to tweak every bit of your message - this seems like the way to go.
Marc

Answer 2

You can't return an anonymous type from any method, can you? So why would you be able to return it from WCF?

Answer 3

Looks like you cannot do so with the XML Serializer because of some complaint about a parameterless constructor but it works for the json serializer if you are serving to an ajax client as indicated by Dave Ward.

Answer 4

OK, I understand. But then if I define
a type - MyObj - for this purpose and
mark its members IsRequired=false, how
can I create+send across an instance
of MyObj with only some of its
members? Is this possible??
Take a look at [DataMember(EmitDefaultValue=false)]

Answer 5

No, it is not. You'll have to define your types ahead of time.

Answer 6

You definitely can return anonymous types. This works, for example:
public object GetLatestPost()
{
XDocument feedXML = XDocument.Load("http://feeds.encosia.com/Encosia");
var posts = from feed in feedXML.Descendants("item")
select new
{
Title = feed.Element("title").Value,
Link = feed.Element("link").Value,
Description = feed.Element("description").Value
};
return posts.First();
}
If you call that method as an ASMX ScriptService's WebMethod, you'll get this JSON from it:
{"d":
{"Title":"Using an iPhone with the Visual Studio development server",
"Link":"http://feeds.encosia.com/~r/Encosia/~3/vQoxmC6lOYk/",
"Description":" Developing iPhone-optimized portions of an ASP.NET ..."}}
You can use a return type of IEnumerable to return a collection of anonymous types also.

Answer 7

You can use the ExpandoObject. When you define a property in a DTO as ExpandoObject the client is generated as Dictionary:
Contract DTO
public class TaskDTO
{
public string Type { get; set; }
public ExpandoObject Args { get; set; }
public string Id { get; set; }
public TaskDTO SuccessTask { get; set; }
public TaskDTO FailTask { get; set; }
public bool IsFinal { get; set; }
}
Client
using (var client = new JobServiceClient())
{
var task = new TaskDTO
{
Id = Guid.NewGuid().ToString(),
Type = "SendEmailTask",
IsFinal = true
};
dynamic args = new ExpandoObject();
args.To = "who#mail.com";
args.Title = "test job service";
args.Content = "test job service";
task.Args = ((IDictionary<string, object>)args).ToDictionary(i => i.Key, i => i.Value);
client.Execute(task);
}
Service
dynamic args = dto.Args;