Hi,

I've got a javascript function that passes a JSON object to a method on a .svc endpoint. The object is sends would look like this

obj = { "Name" : name, "Longitude" : longitude, "Latitude" : latitude };

so to use the service I would use

MyApp.Web.PlaceService(obj, successCallback)

as a bare mininum. Problem is that I would sometimes like to pass

obj = { "Name" : name, "Longitude" : longitude, "Latitude" : latitude, "Radius" : radius };

These correspond to two c# types I have (LocationPoint, and LocationPointWithRadius) and, guess what, the radius one derives from the LocationPoint. The problem I'm having is that I really pass

obj = { Place : new Array({ "Name" : name, "Longitude" : longitude, "Latitude" : latitude, "Radius" : radius }...) } (with or without the radius)

I've tried adding the __type attribute to the item in 'Place,' when I want to add a location point with a radius but the serialiser doesn't make sense of it. I have tried adding the known type attributes all over the place but still the deserialiser cant sort it out. Can anyone give me a few pointers, even if it is just some ways to debug as this all seems to be taken care of before my devenv can spot it.

Many thanks,

tortuga

Ok, so I was doing a couple of things wrong.

First up, when I create the object in javascript, it's no use trying to fudge the __type attribute. What you end up with is a LocationPointWithRadius that got instantiated as a LocationPoint. The key is to look at the js output of the svc file.

Some way down the generated script is a var "gtc" and below this is the registration of the types that your endpoint exposes. This is why specifying ServiceKnownTypeAttribute makes a difference, you can easily see the type that is going to be required when you run the service. So I stopped trying to hack it and rewrote the javascript to create the type at runtime like so;

var test = new MyCompany.Project.Web.Services.LocationPointWithRadius(); //go on to poulate the fields of this object.

or;

var test = new MyCompany.Project.Web.Services.LocationPoint(); //go on to poulate the fields of this object.

I have to decorate the service with the derived type in ServiceKnownTypeAttribute(LocationPointWithRadius), as the method only exposes the LocationPoint. In my case the Place object contains a List<LocationPoint>, so this is how the service javascript knows about the base type, the decoration tells it to expect the derived type too. 

Now I can see how this works it is the coolest thing, but I know my understanding is very basic. However I can build my place object in javascript containing a collection of LocationPoints with or without radius, and it works, so happy days. Please add to this thread if you can help me and others to understand.

Thanks,

tortuga