EF 6自动生成的数据库模型不适用于Web API 2

Question

I have a problem with generating a Web API 2. I'm creating a web API 2 for an existing database, the problem is I don't know fix the following problem: I'm creating a controller for my Sales table(but it has multiple foreign keys):

Table model for FactSale:

    public partial class FactSale
{
    public int FactSalesKey { get; set; }
    public Nullable<int> Quantity { get; set; }
    public decimal Amount { get; set; }
    public Nullable<decimal> AmountForeignCurrency { get; set; }

    public virtual DimCategory DimCategory { get; set; }
    public virtual DimDate DimDate { get; set; }
    public virtual DimDistributor DimDistributor { get; set; }
    public virtual DimRepresentative DimRepresentative { get; set; }
    public virtual DimUser DimUser { get; set; }
}

My auto-generated SalesContoller:

    public class SalesController : ApiController
    {
    private UniscoreDB db = new UniscoreDB();


    // GET api/Sales
    public IQueryable<FactSale> GetFactSales()
    {
        return db.FactSales;
    }
    }

This gives the following error: Type System.Data.Entity.DynamicProxies.FactSale_F6D0DDE3C293539DB57038CFC017F6A6566DEBB69E0AEA2C55DEC5761356A5C3' with data contract name 'FactSale_F6D0DDE3C293539DB57038CFC017F6A6566DEBB69E0AEA2C55DEC5761356A5C3:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. Type System.Data.Entity.DynamicProxies.FactSale_F6D0DDE3C293539DB57038CFC017F6A6566DEBB69E0AEA2C55DEC5761356A5C3' with data contract name 'FactSale_F6D0DDE3C293539DB57038CFC017F6A6566DEBB69E0AEA2C55DEC5761356A5C3:http://schemas.datacontract.org/2004/07/System.Data.Entity.DynamicProxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

I fixed this error by adding the following in my Context: base.Configuration.ProxyCreationEnabled = false;

The problem then becomes the that, for example, DimCategory values are not visible in my JSON string. Now I'm searching for an easy solution to still get the proxy of my table in the JSON, or a better solution then disabling the ProxyCreationEnabled.

Thanks, Phoenix

Answer 1

In the case you might want to use OData you should stick to the following:

I think what you actually want is to use expanding to tell the service you actually want to load those navigation properties too.

You can read about that here: http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/using-$select,-$expand,-and-$value

In your particular case, that would just come to add a [Queryable] attribute on the collection getter and modifying your query to (for example):

GET http://localhost/api/Sales?$expand=DimCategory,DimDate

---

If you would like to stick with the "standard" web api 2 controller ApiController then I belive you will need to specify the properties to include in the code:

// GET api/Sales
public IQueryable<FactSale> GetFactSales()
{
    return db.FactSales
             .Include(x => x.DimCategory)
             .Include(x => x.DimDate)
             // ...and more if you need so...
             .AsQueryable();
}

---

I'd really recomment switching to OData ( http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/odata-v4/create-an-odata-v4-endpoint ) if you can afford to! It's well tought and quite clean, and you get a tremendous amount of client-side control!

Answer 2

Without seeing your full schema it is hard to say exactly, but a common reason for this error is "Loop Handling". Essentially, if you have an object which references another object which in turn references the first object again, it can create a loop that the JSON serializer cannot parse.

Try adding GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore; to your Global.asax.