使用EntityState.Modified的EF更新 [英] EF Update using EntityState.Modified

问题描述

通常我正在使用此代码

Member member = ctx.Members.Find(id);
member.Name = txtName.Text;
ctx.Entry(member).State = EntityState.Modified;
ctx.SaveChanges();

我在 SO 上找到了一个不使用 EntityState.Modified 来更新模型。我尝试删除该行，但该行仍然有效。使用 EntityState.Modified 而不使用 EntityState.Modified 的优缺点是什么？

when I want to update the model using entity framework. I found an example on SO that doesn't use EntityState.Modified to update the model. I try to remove the line and it's still working. What is the pros and cons use EntityState.Modified and doesn't use EntityState.Modified?

注意：我在WinForms中首先使用Entity Framework 6代码

Notes: I'm using Entity Framework 6 Code First in WinForms

推荐答案

EntityState .Modified在您的情况下是无用的，因为当您从上下文中检索要更新的实体时，上下文已经对其进行了跟踪。

The EntityState.Modified is useless in your case because the entity your are updating is already tracked by the context as you retrieve it from the context.

在以下不从上下文中检索实体的情况下，您将需要它：

You would need it in the following scenario where you don't retrieve your entity from the context :

Member member = new Member({Id=1, Name="member"}) ;
context.Entry(member).State = EntityState.Modified; 
context.SaveChanges();

此外，如先前答案中所指定，您的上下文有时仅跟踪数据库的有限视图因此，您需要像上面一样手动初始化跟踪。

Also, as specified in previous answer, your context sometimes tracks only a limited "view" of the database and therefore you need to init the tracking manually like above.

Microsoft文档

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