c# - Linq to Entities 删除而不获取

Question

这段代码可以吗:

using(DbContext db = new DbContext())
{
    IEnumerable<Setting> settings = db.Settings.Where(s=> s.UserId==Uid);
    db.Settings.RemoveRange(settings); 
}

以某种不需要先获取的方式编写？像这样的东西:

using(DbContext db = new DbContext())
{
    db.Settings.Remove(s=> s.UserId==Uid); 
}

Answer 1

当然可以:

如果 UserId 是主键:

using(DbContext db = new DbContext())
{
    Setting settingToRemove = new Setting { UserId = Uid };
    db.Entry(settingToRemove).State = EntityState.Deleted;
    db.SaveChanges();
}

如果 UserId 不是键您必须查询数据库，但您需要的只是根据 UserId 获取主键。

using(DbContext db = new DbContext())
{
    List<int> settingIdsToRemove = db.Setting
        .Where(m => m.UserId == Uid)
        .Select(m => m.Id)
        .ToList();

    foreach(int settingId in settingIdsToRemove)
    {
        Setting settingToRemove = new Setting { Id = settingId };
        db.Entry(settingToRemove).State = EntityState.Deleted;
    }

    db.SaveChanges();
}