WebAPI OData and customizing navigation links

Question

I'm working on building a WebAPI based OData service and I’m having issues with navigation links. Basically I have two classes where one has a reference to another. When I request either atom or verbose JSON I can see that I have a link between the two. However, I’d like to customize the uri to have it point to a different location rather than the default assumed by the OData library.

Using a simple example, assume that I have two entity sets called ‘entity1’ and ‘entity2’. These are exposed as OData services located at: /api/entities1 and /api/entities2 respectively.

Here’s my sample model code:

public class Entity1 {
  public int ID { get; set; }
  public string Name { get; set; }
  public virtual Entity2 OtherEntity { get; set; }
}

public class Entity2 {
  public int ID { get; set; }
  public string Value { get; set; }
}

I’m using the ODataConventionModelBuilder to register these as follows:

ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
builder.EntitySet<Entity1>("entities1");
builder.EntitySet<Entity2>("entities2");
IEdmModel model = builder.GetEdmModel();
config.Routes.MapODataRoute(routeName: "OData", routePrefix: "api", model: model);

I've implemented the controller as an EntitySetController. All of this works as expected and I get the following response when I request verbose JSON:

{
  "d": {
    "results": [{
      "__metadata": {
        "id": "http://localhost:37826/api/entities1(1)",
        "uri": "http://localhost:37826/api/entities1(1)",
        "type": "ODataSample.Models.Entity1"
      },
    "OtherEntity": {
        "__deferred": {
          "uri": "http://localhost:37826/api/entities1(1)/OtherEntity"
        }
      },
      "ID": 1,
      "Name": "First Entity"
    }]
  }
}

What I’d like to do is to have the ‘OtherEntity’ field in an Entity1 instance refer to the associated Entity2 instance under /api/entities2 so that the link appears something like /api/entities2(2) (assuming the ID of the Entity2 instance is '2').

I know that I could just make the type of ‘OtherEntity’ a Uri and insert the appropriate value in my controller but that seems a bit of a hack (but I could be wrong). From what understand about OData, I believe the right way to do this is to modify the navigation property but I’m not sure how or where.

Any help is appreciated. Thanks in advance.

Cheers, Steve

Javier Javier · Accepted Answer · 2013-07-24T18:15:02

You could do something like the following:

        var entities1 = builder.EntitySet<Entity1>("Entities1");
        entities1.HasNavigationPropertyLink(entities1.EntityType.NavigationProperties.First(np => np.Name == "OtherEntity"),
            (context, navigation) =>
            {
                return new Uri(context.Url.ODataLink(new EntitySetPathSegment("Entities2"), new KeyValuePathSegment(context.EntityInstance.OtherEntity.Id.ToString())));
            }, followsConventions: false);

WebAPI OData and customizing navigation links

1 Answers