Entity Framework 出现 "此 ObjectContext 实例已释放，不可再用于需要连接的操作"

错误的写法:

public static List<Answer> GetAnswer_ByQuestionID(int questionID)

{
 　　using (IA2SContext context = new IA2SContext())
     {

          var list = (from o in context.Answer

              where o.QuestionID == questionID

              select o).ToList();

          return list;

     }

}

解决方案:(.ToList<Answer>())

public static List<Answer> GetAnswer_ByQuestionID(int questionID)

{

 　　using (IA2SContext context = new IA2SContext())

     {

          var list = (from o in context.Answer

              where o.QuestionID == questionID

              select o).ToList<Answer>();

          return list;

     }

}

第二种就是查询的时候包含另一张表:

解决方案:(.Include("Answer"))

public static List<Question> GetQuestionList_ByCategoryID(int categoryID)

{

      using (IA2SContext context = new IA2SContext())

      {

           var list = (from o in context.Question.Include("Answer")

               where o.CategoryID == categoryID && o.IsActive == true

               select o).OrderBy(p => p.SortOrder).ToList<Question>();

           return list;

          }

     }

}