WCF and Anonymous Types

I want to return an anonymous type over WCF. Is this poss开发者_C百科ible?

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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

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

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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.

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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)]

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

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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.

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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;