Effort.Exceptions.EffortException：數據庫尚未初始化 - 非提交更新後？

為什麼會發生這種異常？這是一個錯誤嗎？

我正在使用Effort，EF測試庫來創建我的數據庫的內存實例，並遇到這個有趣的場景：

1. 打開DbContext1
2. 添加項目到Table （不保存）
3. 關閉DbContext1
4. 打開DbContext2
5. 計算Table項目

Effort.Exceptions.EffortException : Database has not been initialized.

但是，如果我也在DbContext1執行計數（步驟5），那麼DbContext2中的Count不會失敗？

完整代碼 ：

public void TestEF()
{
   var factory = new InMemoryMyApplicationDbContextFactory();

   using (var db = factory.CreateDbContext())
   {
      //uncomment this line to prevent exception - why????
      //db.Orders.Count();

      db.Orders.Add(new Order{ Id = Guid.NewGuid() }); 

      // intentionally do not call db.SaveChanges()
   }

   using (var db = factory.CreateDbContext())
   {
      // throws an exception if no read was performed above
      db.Orders.Count();
   }    
}    

完全例外：

public void TestEF()
{
   var factory = new InMemoryMyApplicationDbContextFactory();

   using (var db = factory.CreateDbContext())
   {
      //uncomment this line to prevent exception - why????
      //db.Orders.Count();

      db.Orders.Add(new Order{ Id = Guid.NewGuid() }); 

      // intentionally do not call db.SaveChanges()
   }

   using (var db = factory.CreateDbContext())
   {
      // throws an exception if no read was performed above
      db.Orders.Count();
   }    
}