Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
?
Solved

delete collection with entity framework 4 self traking

Posted on 2010-08-15
2
Medium Priority
?
1,370 Views
Last Modified: 2013-11-11
Hi all,
I'm having  some problem deleting entities that contain collections.
Let's say I have an entity called User that contains the following properties: BankAccount, Appointments (that is a List of Appointment), and Friends (list of Friend).
I have to delete (possibly in one call to the db) al the graph.
The function to delete the user is something like that:

public bool DeleteUser(int userId)
{
                    var user = context.Users
                                        .Include("BankAccount")
                                        .Include("Appointments ")
                                        .Include("Friends ")
                                        .Where(u => u.Id == userId)
                                        .FirstOrDefault();
                    if (user != null)
                    {
                        if (user.BankAccount!= null)
                        {
                            context.DeleteObject(user.BankAccount);
                        }

                        // Until the code above all fine.
                        // Now the problem starts deleting the collections
                        // If I use the following if
                        // I have an exception saying that user.Appointments doesn't exist on the context

                        if (user.Appointments != null)
                        {
                            context.DeleteObject(user.Appointments);
                        }

                        // If I use the following doesn't work because of course the enumeraion changes after the first deleting

                        if (user.Appointments != null)
                        {
                            foreach (var appointment in user.Appointments )
                                   context.DeleteObject(appointment);
                        }

                        context.DeleteObject(user);
                        context.SaveChanges();
                    }
}

Open in new window


So which is the best way of deleting entities with properties that are collections?
Also there is any way of saying: this is the main entity, delete it with all the connected entities in just one line? Something like: context.DeleteObject(user) and all the connected collection are deleted?
I'm using EF 4 and self tracking T4 template.

Thanks
0
Comment
Question by:xtremereality
2 Comments
 
LVL 3

Accepted Solution

by:
with earned 2000 total points
ID: 33446570
for (int i = user.Appointments.Count() - 1; i > -1; i--)
      context.DeleteObject(user.Appointments[i]);

Try walking the collection "backwards" by index, deleting from last to first.

This is a useful technique to remember for times when you must iterate over a collection for the purposes of removing items from that collection.  It's works because you do not invoke an IEnumerator (because you do not use foreach), and if the list changes size, it's ok because because loop variable i is always getting smaller.
0
 
LVL 25

Expert Comment

by:apeter
ID: 33447661
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

A long time ago (May 2011), I have written an article showing you how to create a DLL using Visual Studio 2005 to be hosted in SQL Server 2005. That was valid at that time and it is still valid if you are still using these versions. You can still re…
Calculating holidays and working days is a function that is often needed yet it is not one found within the Framework. This article presents one approach to building a working-day calculator for use in .NET.
This Micro Tutorial will teach you how to add a cinematic look to any film or video out there. There are very few simple steps that you will follow to do so. This will be demonstrated using Adobe Premiere Pro CS6.
Integration Management Part 2
Suggested Courses
Course of the Month10 days, 2 hours left to enroll

569 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question