如何使用EF 6.1.1从表中删除单个记录 [英] How do i delete single record from table using EF 6.1.1
问题描述
我正在使用实体框架6.1.1。
我是删除单记录从表如下，但我不知道是否是唯一的方式或可以进一步重写它有效的方式。
I am deleting single record from table as following but i am not sure whether its the only way or could further rewrite it in an efficient way.
有人可以分享评论？
原因：我是问，因为早期帖子中的许多解决方案都是指EF 4.0而不是使用最新版本6.1.1。
Reason: I am asking because many solutions in earlier posts are referring to EF 4.0 and not using the latest version 6.1.1.
Guid studentId = student.Id;
StudentReportDetail stuDetails = _context.StudentReportDetail.Find(studentId);
if (stuDetails != null)
{
_context.StudentReportDetail.Remove(stuDetails);
_context.SaveChanges();
}
推荐答案
删除EF 4和EF 6之间的实体。要使用Entity Framework删除实体，您需要在 DbSet 删除方法C $ C>。 删除适用于现有和新添加的实体。
There are no changes about how to delete an entity between EF 4 and EF 6. To delete an entity using Entity Framework, you need to use the Remove method on DbSet. Remove works for both existing and newly added entities.
-
调用
删除保存
到数据库将取消添加实体。实体是
从更改跟踪器中删除，不再被
DbContext跟踪。
调用删除在正在更改跟踪的现有实体上
将在下次注册该实体删除 SaveChanges 被调用
。
Calling Remove on an existing entity that is being change-tracked
will register the entity for deletion the next time SaveChanges is
called.
数据库
作为您在问题中显示的示例，您需要先从上下文加载现有实体以将其删除。如果您不知道 Id ，您可以执行一个查询，如下所示：首先找到它：
As the example you show in your question, you need to load first the existing entity from your context to delete it. If you don't know the Id, you can execute a query as I show below to find it first:
var report= (from d in context.StudentReportDetail
where d.ReportName == "Report"
select d).Single();
context.StudentReportDetail.Remove(report);
context.SaveChanges();
删除而不从数据库加载
如果您需要删除一个实体，但它尚未在内存中，那么从数据库中检索该实体只是为了将其删除，这样做有点低效。如果您知道要删除的实体的密钥，则可以附加表示要删除的实体的存根，然后删除该存根。一个存根是一个实体，它只分配了键值。
If you need to delete an entity, but it’s not already in memory, it’s a little inefficient to retrieve that entity from the database just to delete it. If you know the key of the entity you want to delete, you can attach a stub that represents the entity to be deleted, and then delete this stub. A stub is an instance of an entity that just has the key value assigned. The key value is all that’s required for deleting entities.
var toDelete = new StudentReportDetail {Id = 2 };
context.StudentReportDetail.Attach(toDelete);
context.StudentReportDetail.Remove(toDelete);
context.SaveChanges();
其他方法可能会将实体的状态更改为已删除。 DbContext 具有名为 Entry 和 Entry< TEntity> ，这些方法得到给定实体的 DbEntityEntry ，并提供对实体的信息的访问，并返回一个 DbEntityEntry EntityState.Deleted ：
Other way could be changing the entity's state to Deleted.DbContext has methods called Entry and Entry<TEntity>, these methods get a DbEntityEntry for the given entity and provide access to the information about the entity and return a DbEntityEntry object able to perform the action on the entity. Now you can perform the delete operation on the context by just changing the entity state to EntityState.Deleted:
var toDelete = new StudentReportDetail {Id = 2 };
context.Entry(toDelete).State = EntityState.Deleted;
context.SaveChanges();
使用第三方库
另外还有一种方法是使用第三方库， EntityFramework Plus 有一个可以安装的块包。您可以使用批量删除操作：
There is another way but is using a 3rd party library, EntityFramework Plus, there is a nugget package you can install. You can use the batch delete operation:
context.StudentReportDetail
.Where(u => u.Id== stuDetails)
.Delete();
这篇关于如何使用EF 6.1.1从表中删除单个记录的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
