具有Linq.Dynamic的C＃实体框架：按COALESCE排序

Question

I got two tables, dbo.Foo and dbo.Bar .

dbo.Foo got two important properties:

• ID (Primary key)
• OwnerID (Foreign key to the same table (ID))

dbo.Bar got three important properties:

• ID (Primary key)
• FooID (Foreign key to dbo.Foo (ID))
• FooOwnerID (Foreign key to dbo.Foo (ID) too)

In dbo.Bar , FooID OR FooOwnerID has to be set. Below I created a graphic to show the structure:

My model class for dbo.Bar looks like:

public class Bar
{
    public int ID { get; set; }
    public int FooID { get; set; }
    public int FooOwnerID { get; set; }

    public virtual Foo Foo { get; set; }
    public virtual Foo FooOwner { get; set; }
}

The mapping for the table (using the fluent-api) looks like:

modelBuilder.Entity<Bar>().ToTable("Bar", "dbo");
modelBuilder.Entity<Bar>().HasKey(x => x.ID);
modelBuilder.Entity<Bar>().Property(x => x.FooID).IsRequired();
modelBuilder.Entity<Bar>().Property(x => x.FooOwnerID).IsRequired();
modelBuilder.Entity<Bar>().HasOptional(x => x.Foo).WithMany().HasForeignKey(x => x.FooID);
modelBuilder.Entity<Bar>().HasOptional(x => x.FooOwner).WithMany().HasForeignKey(x => x.FooOwnerID);

This works. But I want to have FooOwner to be the actual owner of Foo instead of null if only FooID is set. Does someone have a idea how to do this?

Background

I am using DataTables to display the data at the view. To order the items, DataTables sends the name of the column to order ( Foo.ID for example). I am using Linq.Dynamic to order the result set dynamically. An order string look like this: Foo.ID asc, PropertyOfBar desc .

Answer 1

Does someone have a idea how to do this?

Nothing built-in. But you can always use a method or a NotMapped property

eg

public Foo GetFooOwner() => FooOwner??Foo.Owner;