Refresh ObservableCollection

Question

Hi,

Well i create one observableCollection with data of my dataclasses, but when changed data in my dataclasses (Linq To SQL), the observableCollection don't refresh and i need do this to force the refresh:

this.UsersObservable = null;
this.UsersObservable = new ObservableCollection<Users>(DataClasses.Users); 

How i solve the problem in the best way?

How i Bind the observableCollection with my table in the DataClasses?

 

Answer 1

Thiago,

ObservableCollection notifies the UI of any changes to it. As far as I know when you set the collection to null, you destroy the collection and may also lose the binding. I think your best choice is to clear the data and add the new records.

 

Hope this helps.

 

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noorbakhsh حميد نوربخش

Answer 2

But the problem is when two users silmultaneous use my program, the DataClasses when changed by one user refresh in the other user automatic, but the observableCollection don't refresh with the DataClasses.

Answer 3

The code
    this.UsersObservable = new ObservableCollection<Users>(DataClasses.Users);   
initializes the ObservableCollection by enumerating DataClasses.Users and copying the items.   It takes a snapshot.   The OC doesn't listen for change notifications from DataClasses.   It can't - it never saw DataClasses, but only an IEnumerable obtained from DataClasses.Users.   And it's moot anyway, since Linq doesn't even raise change notifications.

To put it another way, changes you make to DataClasses don't magically appear in DataClasses.Users, and even if they did they don't appear in the snapshot that you used to create the ObservableCollection.   

Answer 4

Hi Sam,

I don't undestand your answer.

My problem not have solution?

Answer 5

ObservableCollection only raise event changes for changes in the collection (Add, remove, move and clear element).

It does not raise changes when you update properties of a contained class.

To do what you want you will need implement INotifyPropertyChanged in the User class and raise the PropertyChanged event in each setter.

 

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http://weblogs.asp.net/marianor/

Answer 6

Hi Mariano,

I Think that you don't undestand my problem, i know all this about the ObservableCollection, but my problem is the link of my observableCollection with my Table in DataClasses(Linq To Sql).

Don't have how bind and i need one solution. 

Answer 7

You can try update in this way:

var view = CollectionViewSource.GetDefaultView(this.UsersObservable);
view.Refresh();

 

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http://weblogs.asp.net/marianor/

Answer 8

Hi Mariano,

I Tried this but don't work.

 

Answer 9

Hi Mariano,

I Tried this but don't work.

 

Answer 10

Are you using that observable collection as Source of a Binding ?

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http://weblogs.asp.net/marianor/

Answer 11

Yes.

Answer 12

I think I misanderstood your problem. I am assuming that each time that you need to update your users collection you are creating a new collection, if that is the case the just implement INotifyPropertyChanged in the class containing UsersObservable property and raise the propertyChanged event for that collection:

this.UsersObservable = new ObservableCollection<Users>(DataClasses.Users);
// Raise PropertyChanged event in "UsersObservable"

---

http://weblogs.asp.net/marianor/

Answer 13

Mariano,

I yet did this but don't work.

public ObservableCollection<Users> UsersObservable
        {
            get { return _UsersObservable; }
            set
            {
                if (_UsersObservable != value)
                {
                    _UsersObservable = value;
                    OnPropertyChanged("UsersObservable");
                }
            }
        }

Answer 14

I'm probably not understanding the problem correctly either, but if you're expecting your database to update the ObservableCollection it well, just won't as far as I know. You could try using a DispatchTimer that calls OnPropertyChanged("UsersObservable"); and see if that does the trick....

Answer 15

Hi MSearles

 

I think this good solution for me, but if i do DispatchTimer,

I'll have to do this?

 

this.UsersObservable = null;
this.UsersObservable = new ObservableCollection<Users>(DataClasses.Users);

Answer 16

You need to notify the UI that the ObservableCollection has changed. When you 'new' the variable, the UI is no longer looking at the original collection, so you have to manually tell it where to look again, and you do that with the INotifyPropertyChanged interface like so..

XAML

 

<ListView ItemsSource="{Binding Users}"></ListView>

 

CODE BEHIND

 

using System.Collections.ObjectModel;

using System.Windows.Threading;

using System.ComponentModel;

/// <summary>

/// Interaction logic for Window1.xaml

/// </summary>

public partial class Window1 : Window, INotifyPropertyChanged

{

    DispatcherTimer _refreshTimer = new DispatcherTimer();

    ObservableCollection<string> _users = new ObservableCollection<string>();

    List<string> _dummyDataClass = new List<string>();

    int _dummyDataIndex;

 

    public Window1()

    {

        InitializeComponent();

 

        _refreshTimer.Interval = TimeSpan.FromSeconds(2);

        _refreshTimer.Tick += new EventHandler(_refreshTimer_Tick);

        _refreshTimer.Start();

 

        this.DataContext = this;

 

    }

 

    public ObservableCollection<string> Users

    {

        get { return _users; }

        set

        {

            _users = value;

 

            OnPropertyChanged("Users");

        }

    }

 

    void _refreshTimer_Tick(object sender, EventArgs e)

    {

        _dummyDataClass.Add(string.Format("Item {0}", _dummyDataIndex++));

        Users = new ObservableCollection<string>(_dummyDataClass);

    }

 

    #region INotifyPropertyChanged Members

 

    public event PropertyChangedEventHandler PropertyChanged;

 

    public void OnPropertyChanged(string name)

    {

        if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(name));

    }

 

    #endregion

}

Warm regards,

Matt

Answer 17

Hi MSearles,

Good Idea, you solved my problem.