breeze projection : error selecting non scalar navigation properties

问题

Ho to everybody. Below you can see the partial result of the EF Power Tools reverse engineering made on the database of mine.

public partial class Articoli {        
    public decimal Id_Articolo { get; set; }
    public string Codice { get; set; }
    public virtual ICollection<Udc_Dettaglio> FK_Udc_Dettaglio_Articoli { get; set; }
}

public partial class Udc_Dettaglio {
    public decimal Id_Udc { get; set; }
    public decimal Id_Articolo { get; set; }
    public virtual Articoli FK_Udc_Dettaglio_Articoli { get; set; }
}

public Udc_DettaglioMap() {
    // Primary Key
    this.HasKey(t => new { t.Id_Udc, t.Id_Articolo });

    // Relationships
    this.HasRequired(t => t.FK_Udc_Dettaglio_Articoli)
        .WithMany(t => t.FK_Udc_Dettaglio_Articoli)
        .HasForeignKey(d => d.Id_Articolo);        
}

If, by using breeze, i try to perform this query

breeze.EntityQuery.from("Articoli").expand("FK_Udc_Dettaglio_Articoli")

or this one

breeze.EntityQuery.from("Articoli").select("Codice,FK_Udc_Dettaglio_Articoli")

everything works fine, but if i try with this

breeze.EntityQuery.from("Articoli").select("Codice,FK_Udc_Dettaglio_Articoli.Id_Udc")

it throw an exeption :

Unable to locate property 'Id_Udc' on type 'System.Collections.Generic.ICollection`1[AWM.Models.Udc_Dettaglio]'."

Am I missing something in EF model definition ? i guess not because expand utility is working ...

回答1:

I believe you are trying to build a query that EF doesn't support (and that OData query syntax doesn't support either).

Your FK_Udc_Dettaglio_Articoli is a collection navigation property of Articoli. By trying to go after just the Id_Udc property of each element in that collection, you are actually trying to create a projection within a projection ... and EF doesn't support that as far as I know.

To verify, try to construct a LINQ query on the server side that does what you want. Something like

dbContext.Articoli.Select(
    a => new {a.Codice, a.FK_Udc_Dettaglio_Articoli.Select(f => new {f.Id_Udc}));

You'll quickly discover that that query does not compile. You get a message something like "anonymous type projection initializer should be simple name or member access expansion".

来源：https://stackoverflow.com/questions/21531964/breeze-projection-error-selecting-non-scalar-navigation-properties

标签

entity-framework

breeze