AcceptAllChanges 导致实体框架...不接受更改？
我正在使用.NET 3.5 SP1。我有一个简单的脚本来删除一些实体。
var people = (from Person p in context.People
where p.FirstName == "Testy" &&
p.LastName == "McTesterson"
select p).ToList();
people.ForEach(p => context.DeleteObject(p));
//context.AcceptAllChanges();
context.SaveChanges();
如果我取消注释 AcceptAllChanges()，则不会删除对象。如果我保留它的评论，实体将被删除。为什么 EF 会有这样的表现？这似乎适得其反。
I'm using .NET 3.5 SP1. I have a simple script that deletes some entities.
var people = (from Person p in context.People
where p.FirstName == "Testy" &&
p.LastName == "McTesterson"
select p).ToList();
people.ForEach(p => context.DeleteObject(p));
//context.AcceptAllChanges();
context.SaveChanges();
If I uncomment AcceptAllChanges(), the objects are not deleted. If I keep it commented, the entities are deleted. Why does EF behave like this? It seems counter productive.
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这就是
AcceptAllChanges的行为。接受更改会“重置”ObjectContext的内部状态。这意味着添加或修改的所有实体都设置为“未更改”状态，并且删除的所有实体都从上下文中分离。相比之下，
SaveChanges方法会迭代ObjectContext的内部状态，并为状态为“已添加”的每个实体创建 INSERT db 命令，为每个实体创建 UPDATE db 命令每个处于“已修改”状态的实体和每个处于“已删除”状态的实体的 DELETE db 命令。SaveChanges默认情况下会在执行所有命令后接受所有更改。如果您在
SaveChanges之前运行AcceptAllChanges，则会清除所有更改，并且数据库中不会执行任何操作。该方法存在的原因是您可以关闭默认的 SaveChanges 行为；在这种情况下，您必须在执行SaveChanges后手动接受更改。否则，下次调用SaveChanges将再次执行更改。That is the behavior of
AcceptAllChanges. Accepting changes "resets" the internal state ofObjectContext. It means that all entities which were added or modified are set to "unchanged" state and all entities which were deleted are detached from the context.In contrast,
SaveChangesmethod iterates the internal state ofObjectContextand creates INSERT db commands for each entity with a state of added, UPDATE db command for each entity in modified state and DELETE db command for each entity in deleted state.SaveChangesby default accepts all changes after it executes all commands.If you run
AcceptAllChangesbeforeSaveChangesyou clear all changes and there is nothing to execute in DB. The reason why this method exists is that you can turn off defaultSaveChangesbehavior; in such a case, you must accept changes manually after you executeSaveChanges. Otherwise the next call toSaveChangeswill execute the changes again.