Web API 2.2 OData Controller supporting class hierarchy

Question

I'm trying to create an ODataController that supports casting action.

Let's say we have Shape class and Circle class that derives from Shape

namespace NS
{
    public abstract class Shape {    
       int Id; 
       int X;
       int Y; 
     }

     public class Circle : Shape {    
        int Radius;
     }
}

And I want to create controller ShapesController.

public class ShapesController: ODataController
    {
        ShapesContext db = new ShapesContext();

        [EnableQuery]
        public IQueryable<Shape> Get()
        {
            return db.Shapes;
        }
        [EnableQuery]
        public SingleResult<Shape> Get([FromODataUri] int key)
        {
            IQueryable<Shapes> result = db.Shapes.Where(p => p.Id == key);
            return SingleResult.Create(result);
        }
}

Everything work fine for request like

/odata/Shapes
/odata/Shapes(1)

But requests like

/odata/Shapes(1)/NS.Circle

cause 404 error

Referring to routing conventions http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/odata-routing-conventions I have to create action like that

[EnableQuery]
public SingleResult<Circle> GetCircle([FromODataUri] int key)
{
     IQueryable<Shapes> result = db.Shapes.Where(p => p.Id == key).Cast<Circle >;
     return SingleResult.Create(result);
}

But it does not help - 404.

How can i make my controller support casting? Or maybe my approach is completely wrong and I misunderstand the principles?

Thanks

Yi Ding - MSFT Yi Ding - MSFT · Accepted Answer · 2015-05-25T06:45:50

This sample should work for you:

Supposing I have the following model:

public class Product
{
    public int ID { get; set; }
    public string Name { get; set; }
}

public class Category:Product
{
    public int Price { get; set; }
}

I only need to have this two controller actions both in the ProductsController class:

[EnableQuery]
public IHttpActionResult GetProduct([FromODataUri] int key)
{
    return Ok(Proxy.Products.FirstOrDefault(c => c.ID == key));
}

[EnableQuery]
public IHttpActionResult GetCategory([FromODataUri] int key)
{
    return Ok(Proxy.Products.FirstOrDefault(c => c.ID == key));
}

And both

Products(2)/ODataV4Service.Models.Category

and

Products(2)

will be supported with the correct context URLs respectively.

Web API 2.2 OData Controller supporting class hierarchy

2 Answers