.net 实体框架，更新和保存使用SelectMany检索的对象上的更改不起作用

情景1://在这种情况下，训练不会从数据库中删除

Season season = dbContext.Seasons.Find(58);
var ps1 = season.PlannerSeason;
PlannerWorkout pworkoutToRemove = ps1.Weeks.SelectMany(w => w.WeekDays.SelectMany(wd => wd.PlannerWorkouts)).Where(pw => pw.WorkoutID == 3615).FirstOrDefault();
bool isRemoved = ps1.Weeks.SelectMany(w => w.WeekDays.SelectMany(wd => wd.PlannerWorkouts)).ToList().Remove(pworkoutToRemove);

dbContext.SaveChanges(); //does not work

情景2://此处检索完全相同的训练并从db中删除。它起作用了

Season season = dbContext.Seasons.Find(58);
var ps1 = season.PlannerSeason;
PlannerWeek pweek = ps1.Weeks.Find(w => w.WeekNo == 14);
PlannerWeekDay pwd = pweek.WeekDays.Find(d => d.DayNo == 1);
PlannerWorkout pworkoutToRemove = pwd.PlannerWorkouts.Find(pw => pw.WorkoutID == 3615);
bool isRemoved = pwd.PlannerWorkouts.Remove(pworkoutToRemove);

dbContext.SaveChanges(); //works

---

通过SelectMany检索单个对象会有区别吗？

问题不在于使用

SelectMany检索对象，而是在这里

bool isRemoved = ps1.Weeks.SelectMany(w => w.WeekDays.SelectMany(wd => wd.PlannerWorkouts))
    .ToList() // <--
    .Remove(pworkoutToRemove);

换句话说，您正在创建一个临时列表并从该列表中删除对象，而不是像工作示例中那样从父集合中删除对象

如果您对父
工作日
具有反向导航属性，则可以使用此属性

bool isRemoved = pworkoutToRemove != null &&
    pworkoutToRemove.WeekDay.PlannerWorkouts.Remove(pworkoutToRemove);

或者您可以直接从相应的
DbSet
中将其删除：

bool isRemoved = false;
if (pworkoutToRemove != null)
{
    dbContext.PlannerWorkouts.Remove(pworkoutToRemove);
    isRemoved = true;
}

或将实体状态设置为“已删除”

：

bool isRemoved = false;
if (pworkoutToRemove != null)
{
    dbContext.Entry(pworkoutToRemove).State = EntityState.Deleted;
    isRemoved = true;
}

bool isRemoved = false;
if (pworkoutToRemove != null)
{
    dbContext.Entry(pworkoutToRemove).State = EntityState.Deleted;
    isRemoved = true;
}