What is the correct way to find and set the primary key generically with EF Core - asp.net-core

Question

I am trying to access the primary key from a generic parameter on my entity class which is what all of my DB object inhert from.
The following code works. But is it bad practise to access the DBcontext from within the Entity class? If so, how else can I do this? Is there something like IObjectContextAdapter from EF6?
public abstract class Entity
{
private DBContext _context = new DBContext(null);
[NotMapped]
public int ID
{
get
{
return _context.PrimaryKeyValueInt(this);
}
set
{
_context.PrimaryKeyProperty(this).PropertyInfo.SetValue(this, value);
}
}
}

Answer 1

So, I assume you have a bunch of entity classes with various names for their primary keys, like DoodadId, WidgetId, etc. and want them all to extend a base class with a single property to access the primary key? If so, I've done something like that with Attributes and Reflection. Create an Attribute to use to identify Primary Key properties:
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
public class EntityIdAttribute : Attribute
{
}
Then create the base class and add the property to it. In my case I use Guid for primary keys:
public abstract class Entity
{
[NotMapped]
public virtual Guid EntityId
{
get
{
return (Guid)EntityIdProperty.GetValue(this);
}
set
{
EntityIdProperty.SetValue(this, value);
}
}
private PropertyInfo EntityIdProperty => this.GetType().GetProperties()
.Where(prop => Attribute.IsDefined(prop, typeof(EntityIdAttribute)))
.FirstOrDefault();
}
Then in your entity classes, extend Entity and decorate the primary key property with [EntityId]:
public class Widget : Entity
{
[EntityId]
public Guid WidgetId { get; set; }
// ......
}