objectset

问题 I'm following the MusicStore tutorial I'm already on the Part 8 of the tutorial. I got this error when I tried to add the ShoppingCart class.. I tried to google for a possible solution but failed to find a clean one T_T .. based on my research I'm getting this error because I'm using edmx which is database first instead of code first on the tutorial. I had this codes added and is having an error on Add() and Remove() namespace Project.Models { public partial class ShoppingCart {

问题 Is there a way to get ObjectQuery<T> for specfied generic type? Pseudo: public partial class MyObjectContext { public ObjectSet<TEntity> GetObjectSet<TEntity>() { return Helper.GetObjectSet<TEntity>(this); } } 回答1: Yes this is what you need: public partial class MyObjectContext { public ObjectSet<TEntity> GetObjectSet<TEntity>() { return this.CreateObjectSet<TEntity>(); } } As you can see your helper method is not needed because you can call CreateObjectSet directly on MyObjectContext

问题 I use: EntityFramework + POCO Here is the thing: public interface IBaseType { int Id { get; set; } } public class BaseType : IBaseType { public virtual int Id { get; set; } } public class DerivedType : BaseType { } The problem: public class EntityFetcher<T> where T : BaseType { public object GetById(int id) { ObjectSet<T> objectSet = (ObjectSet<T>)GetTheObjectSet(typeof(T)); return objectSet.SingleOrDefault((o) => o.Id == id); } } If T is BaseType this all works perfectly, but: The problem is