Question

我需要在Entity Framework中使用内部联接删除一些记录。

例如，我有User，Role和UserRoleMapping表：

User => Id, Name
Role => Id, Name
UserRoleMapping => Id, UserId, RoleId

现在我需要删除属于Id = 2的角色的用户。

我需要触发查询，如下所示

Delete user 
from User 
inner join UserRoleMapping on User.Id = UserRoleMapping.UserId 
where UserRoleMapping.RoleId = 2

这是否可以在实体框架中使用？

Answer 1

在EF中，您需要首先加载实体，选择项目然后DeleteObject。你需要这样做：

using (var context = new YourContext())
{
   var item = (from user in context.User
   join userRoleMapping in context.UserRoleMapping on user.Id equals userRoleMapping.UserId
   where userRoleMapping.RoleId == 2
   select user).ToList().ForEach(context.User.DeleteObject);


   context.SaveChanges();
}

注意：

ObjectContext.DeleteObject(entity)在上下文中将实体标记为已删除。（之后删除了EntityState。）如果之后调用SaveChanges，EF会向数据库发送SQL DELETE语句。如果违反了数据库中的引用约束，则将删除该实体，否则将引发异常

或

using (var context = new YourContext())
 {
    var items = (from user in context.User
    join userRoleMapping in context.UserRoleMapping on user.Id equals userRoleMapping.UserId
    where userRoleMapping.RoleId == 2
    select user).ToList();

    foreach (var item in items)
    {
      context.Entry(item).State = EntityState.Deleted;
    }

    context.SaveChanges();
}

或使用ExecuteStoreCommand，您可以在这里找到more

using (var context = new YourContext())
{
    context.ExecuteStoreCommand("DELETE FROM USER INNER JOIN USERROLEMAPPING ON USER.ID = USERROLEMAPPING.USERID WHERE USERROLEMAPPING .ROLEID = {0}", customId);
}

如何使用Entity Framework中的内部联接删除或更新？

1 个答案: