Asp.Net Web API 2第十八课——Working with Entity Relations in OData

namespace OData.Models
{
    public class Supplier
    {
        [Key]
        public string Key { get; set; }
        public string Name { get; set; }
    }
}

    public class Product
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
        public string Category { get; set; }
        // New code
        [ForeignKey("Supplier")]
        public string SupplierId { get; set; }
        public virtual Supplier Supplier { get; set; }
    }

    public class ProductServiceContext : DbContext
    {
        public ProductServiceContext() : base("name=ProductServiceContext")
        {
        }

        public DbSet<Product> Products { get; set; }

        ///New Code
        public DbSet<Supplier> Suppliers { get; set; }
    
    }

            ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
            builder.EntitySet<Product>("Products");
            // New code:
            builder.EntitySet<Supplier>("Suppliers");

GET /Products(1)/Supplier

        // GET /Products(1)/Supplier
        public Supplier GetSupplier([FromODataUri] int key)
        {
            Product product = db.Products.FirstOrDefault(p => p.ID == key);
            if (product == null)
            {
                throw new HttpResponseException(HttpStatusCode.NotFound);
            }
            return product.Supplier;
        }

/Products(1)/$links/Supplier

POST http://localhost/odata/Products(1)/$links/Supplier
Content-Type: application/json
Content-Length: 50

{"url":"http://localhost/odata/Suppliers('CTSO')"}

[AcceptVerbs("POST", "PUT")]
public async Task<IHttpActionResult> CreateLink([FromODataUri] int key, string navigationProperty, [FromBody] Uri link)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }
            
    Product product = await db.Products.FindAsync(key);
    if (product == null)
    {
        return NotFound();
    }
            
    switch (navigationProperty)
    {
        case "Supplier":
            string supplierKey = GetKeyFromLinkUri<string>(link);
            Supplier supplier = await db.Suppliers.FindAsync(supplierKey);
            if (supplier == null)
            {
                return NotFound();
            }
            product.Supplier = supplier;
            await db.SaveChangesAsync();
            return StatusCode(HttpStatusCode.NoContent);

        default:
            return NotFound();
    }
}

// Helper method to extract the key from an OData link URI.
private TKey GetKeyFromLinkUri<TKey>(Uri link)
{
    TKey key = default(TKey);

    // Get the route that was used for this request.
    IHttpRoute route = Request.GetRouteData().Route;

    // Create an equivalent self-hosted route. 
    IHttpRoute newRoute = new HttpRoute(route.RouteTemplate, 
        new HttpRouteValueDictionary(route.Defaults), 
        new HttpRouteValueDictionary(route.Constraints),
        new HttpRouteValueDictionary(route.DataTokens), route.Handler);

    // Create a fake GET request for the link URI.
    var tmpRequest = new HttpRequestMessage(HttpMethod.Get, link);

    // Send this request through the routing process.
    var routeData = newRoute.GetRouteData(
        Request.GetConfiguration().VirtualPathRoot, tmpRequest);

    // If the GET request matches the route, use the path segments to find the key.
    if (routeData != null)
    {
        ODataPath path = tmpRequest.GetODataPath();
        var segment = path.Segments.OfType<KeyValuePathSegment>().FirstOrDefault();
        if (segment != null)
        {
            // Convert the segment into the key type.
            key = (TKey)ODataUriUtils.ConvertFromUriLiteral(
                segment.Value, ODataVersion.V3);
        }
    }
    return key;
}

public async Task<IHttpActionResult> DeleteLink([FromODataUri] int key, string navigationProperty)
{
    Product product = await db.Products.FindAsync(key);
    if (product == null)
    {
        return NotFound();
    }

    switch (navigationProperty)
    {
        case "Supplier":
            product.Supplier = null;
            await db.SaveChangesAsync();
            return StatusCode(HttpStatusCode.NoContent);

        default:
            return NotFound();

    }
}

DELETE /odata/Customers(1)/$links/Orders(1)

void DeleteLink([FromODataUri] int key, string relatedKey, string navigationProperty);

POST http://localhost/odata/Products(2)/$links/Supplier
Content-Type: application/json
Content-Length: 50

{"url":"http://localhost/odata/Suppliers('WING')"}