How to initialize and manipulate an ObservableCollection in Entity Framework?

Question

I have an ObservableCollection in the ViewModel and I initialize it in the following way:

public ViewModel()
{
    List<T> list = null;

    using (var context = new DbContext())
    {
        list = context.Set<T>().ToList();
    }

    Items = new ObservableCollection<T>(list);
}

And every time I add an item to the context, I add it to the collection too.

public void Add<T>(T obj)
{
    using (var context = new DbContext())
    {
        context.Set<T>().Add(obj);
        context.SaveChanges();
    }

    Items.Add(obj);
}

And when to remove an item from the context, I remove it from the ObservableCollection as well.

There is yet an alternative and I can initialize the ObservableCollection again after the items are added to or removed from the context:

public void Add<T>(T obj)
{
    List<T> list = null;

    using (var context = new DbContext())
    {
        context.Set<T>().Add(obj);
        context.SaveChanges();

        list = context.Set<T>().ToList();
    }

    Items = new ObservableCollection<T>(list);
}

Now I need to know whether which way is better in case of performance and memory management?

Try it yourself and see. Sometimes programmers are like scientists performing interesting experiments — MickyD
Isn't it better to use others' experiences? Anyway, how may I try it? Are there any tools out there to help me with this experiment? — user3530012
Visual Studio has some pretty funky performance tools for some time now. — MickyD

Patrick Patrick · Accepted Answer · 2015-08-20T10:56:36

I would prefer the first pattern because the second reloads all items from the database. This might be the bigger performance issue than re-initializing the collection.

Further I don't see the advantage of using ObservableCollection instead of an ordinary List if you prefer to create a new instance instead of keeping the old one and handling its CollectionChange event which gets fired when adding or removing an element.

How to initialize and manipulate an ObservableCollection in Entity Framework?

1 Answers