当分配null值给它的引用时，子实体不会更新

问题描述

我有一个名为：应用程序的实体，它的实体也是实体的ApplicationStatus ，ApplicationStatus值为yes或no，在Application中为空。

所以当我执行：

 应用程序应用程序= MyEntities.Applications 。第一（）; 
 application.ApplicationStatus = null; 
 MyEntities.SaveChanges（）; 
  

ApplicationStatus不会更新其值，除非我调试它，然后执行快速查看应用程序.ApplicationStatus。

然而

  application.ApplicationStatusId =空值; 
  

工作正常。

为什么这个不起作用：

application.ApplicationStatus = null;

感谢

编辑 / p>

由于@LadislavMrnka答案解决了调试行为，并且与懒惰加载相关的问题：

我们如何解释这些情况？

 应用程序应用程序= MyEntities.Applications.First（）; 
 
 application.ApplicationStatusId = null; //此值更新为db 
 
 ApplicationStatus applicationStatus = MyEntities.ApplicationStatuses.First（a => a.Name ==no）; 
 app.ApplicationStatus = applicationStatus; //这更新db中的值
 
 app.ApplicationStatus = null; //但是这不是
  

解决方案

将工作：

 应用程序应用程序= MyEntities.Applications.Include（ApplicationStatus）。 
  

原因是您的 ApplicationStatus 从未加载。如果您调试和访问它，您的调试访问将触发延迟加载并加载它。

I have an entity named: Application and it has field ApplicationStatus which is entity as well, ApplicationStatus values are yes or no and it's nullable in Application.

So when I execute:

Application application = MyEntities.Applications.First();
application.ApplicationStatus = null; 
MyEntities.SaveChanges(); 

ApplicationStatus won't update its value, unless I debug it and do quick watch application.ApplicationStatus.

However

application.ApplicationStatusId = null;

works fine.

My question, why this one doesn't work:

application.ApplicationStatus = null;

Thanks

EDIT further question:

As @LadislavMrnka answer solves debug behaviour and and the issue related lazy loading:

how can we interpret these situation?

Application application = MyEntities.Applications.First();

application.ApplicationStatusId = null; //This updates value in db

ApplicationStatus applicationStatus = MyEntities.ApplicationStatuses.First(a => a.Name == "no");
app.ApplicationStatus = applicationStatus; //This updates value in db too

app.ApplicationStatus = null; // But this doesn't

解决方案

Use this and it will work:

Application application = MyEntities.Applications.Include("ApplicationStatus").First();

The reason is that your ApplicationStatus was never loaded. If you do debug and access it your debugging access will trigger lazy loading and loads it.

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