CODEWITHSUNDEEP
c#linq
Trevor Daniel
Trevor Daniel

Reputation: 3954

Linq - Rows In Database not Deleting

Looking for some help with linq. I am getting in a right muddle as I think I am doing something fundamentally wrong.

This is the background.

I have a user with a list of activities - the activities have an "ActivityDateTime"

So, what I am attempting to do should be quite easy. I am trying to retrieve a user with a list of activities for a particular date and "replace" any existing ones with the new ones...

But I am getting in a right mess..

here is my code:

public static bool UpdateDailyActivity(string emailAddress, DateTime activityDate) {

        // get a user
        using (DataModel db = new DataModel()) {
            DataUser user = db.DataUsers
                .Include("AuthData")
                .Include("Activities")
                .Include("Activities.activities")
                .Include("Activities.goals")
                .Include("Activities.summary")
                .Include("Activities.summary.distances")
                .Where(x => x.Email == emailAddress).FirstOrDefault();


            // Get a list of todays activities already in the user
            List<Activity> todaysActivities = user.Activities
                .Where(x => x.ActivityDateTime >= activityDate.Date && x.ActivityDateTime < activityDate.AddDays(1).Date)
                .ToList();

            // remove the activities from the user
            var activitiesToRemove = new HashSet<Activity>(todaysActivities);
            user.Activities.RemoveAll(x => activitiesToRemove.Contains(x));

            // save the user to try and remove the current activities
            db.SaveChanges(); // <- this is leaving the rows behind

            // get the activity data
            Activity activityData = GetDailyActivity(user, activityDate);

            if (activityData != null) {

                // update this days activity for this user
                user.Activities = new List<Activity>();
                user.Activities.Add(activityData);

                // save the changes
                db.SaveChanges();

                // everything worked ok
                return true;

            } else {
                // failed
                return false;
            }
        }

    }

I know I am in a mess. Can anyone help me find my way out?

This is what my table looks like in the database after running the above code 3 times...

enter image description here

Upvotes: 0

Views: 49

Answers (1)

Luca Ghersi
Luca Ghersi

Reputation: 3321

Have you checked the State property of the entity after this line of code?

 user.Activities.RemoveAll(x => activitiesToRemove.Contains(x));

There's a chance that all this items are Untracked, that's why probably nothings happen on SaveChanges().

Try this way forcing the State to Deleted. Usually works here :)

// Get a list of todays activities already in the user
        List<Activity> todaysActivities = user.Activities
            .Where(x => x.ActivityDateTime >= activityDate.Date && x.ActivityDateTime < activityDate.AddDays(1).Date)
            .ToList();

                    // remove the activities from the user
        foreach (var a in todaysActivities)
        {  
                db.Entry(a).State = EntityState.Deleted;
        }

and then db.SaveChanges();

Upvotes: 1

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