我可以为实体框架模型创建“中继”或“通用”属性吗？

Question

I hope my wording makes sense... I wasn't quite sure exactly how to explain what I'm looking to do.

I have a method in a generic class that returns a list of entities as follows:

public abstract class ChildCRUDController<TModel> : CRUDController<TModel, ... >
    where TModel : IChildEntity

public ViewResult List(int id)
{
    return View(repository.GetMany(x => x.ParentID == id));
}

This controller is implemented by quite a few other controllers. The issue I have is that not all entities that implement IChildEntity have the same parent type. To get around this issue I created ParentID properties for all the models that implement IChildEntity so they could use the same controller.

public partial class PhoneNumber : IChildEntity
{
    public int ParentID
    {
        get { return CustomerID; }
        set { CustomerID = ParentID; }
    }
}

and...

public partial class Transaction : IChildEntity
{
    public int ParentID
    {
        get { return LeaseID; }
        set { LeaseID= ParentID; }
    }
}

But when I call the List method above I get the following error:

The specified type member 'ParentID' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

Is there any way I can achieve the result I am looking for without pulling the object set into memory or renaming all the properties on the entities themselves?

Thanks!

Answer 1

If you are willing to pass the field name into the List method and to construct your own query you can do it using the techniques described in this StackOverflow article:

• Querying Entity with LINQ using Dyanmic Field Name

Or you could supply the ChildCRUDController with another generic type parameter constrained to an interface that supplies the field name and again use it dynamically.