是否可以从未保存的EF4上下文中看到添加的实体？

Question

我刚刚进入实体框架4,并最终希望使用POCO将其包装在存储库模式中.我发现了一些我没想到的东西.看来,如果您创建上下文,向其添加对象(不保存上下文)并再次查询上下文,则它不会在结果中包含新对象.难道我做错了什么？它似乎应该返回我添加的内容,即使我还没有将结果保存回数据库.这是我的示例代码:

  ShopEntities context = new ShopEntities();

  // there is only 1 customer so far
  var customers = from c in context.Customers
              select c;

  Console.WriteLine(customers.Count()); // displays 1

  Customer newCustomer = context.Customers.CreateObject();
  newCustomer.FirstName = "Joe";
  newCustomer.LastName = "Smith";

  context.Customers.AddObject(newCustomer);

  var customers2 = from c in context.Customers
               select c;

  Console.WriteLine(customers2.Count()); // still only displays 1

  context.SaveChanges();

  var customers3 = from c in context.Customers
               select c;

  Console.WriteLine(customers3.Count()); // only after saving does it display 2

Answer 1

L2E查询始终从DB返回实体.它将根据查询将它们与内存中的更改合并MergeOption.

要查看添加的实体,请查看上下文:

var addedCustomers = from se in context.ObjectStateManager.GetObjectStateEntries(EntityState.Added)
                     where se.Entity is Customer
                     select se.Entity;