Wpf binding when property of the viewmodel is changed - wpf

Question

My wpf project follows the MVVM pattern. In my view-model I have an IList of obejcts which I take from database. Every object from this IList has a property which is List.
When I open the view for that view-model, I have an ItemsControl with this property:
ItemsSource="{Binding TheIListOfObjects}"
and the items in that ItemsControl are actually showing information from List.
So, while the user is on the view, an itemscontrol is shown. What I want to do is this: while on the same view, if the user clicks a button, the List is changed. How can I make the ItemsControl to refresh and show the new info?

Answer 1

All you need to have is ObservableCollection type for the property type.
Xaml
<Window x:Class="Test.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="{Binding RelativeSource={RelativeSource Self}}">
<StackPanel>
<Button Content="Click" Click="Button_Click" />
<ListView ItemsSource="{Binding People}">
<ListView.View>
<GridView>
<GridViewColumn Header="Name" Width="120" DisplayMemberBinding="{Binding Name}" />
</GridView>
</ListView.View>
</ListView>
</StackPanel>
</Window>
Xaml.cs
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private ObservableCollection<Person> _people = new ObservableCollection<Person>();
public ObservableCollection<Person> People
{
get { return _people; }
}
private void Button_Click(object sender, RoutedEventArgs e)
{
People.Add(new Person { Name = "A" });
}
}
public class Person
{
public string Name { get; set; }
}

Answer 2

To make sure that changes in a collection are notified to its bound controls, you must use ObservableCollection<> instead of IList<>

Answer 3

In WPF, once we have data bound a collection to the ItemsSource property of a collection control, we don't refresh the ItemsSource property, or interact with it in any other way. Instead, we work with the data bound property value, so for your example...:
ItemsSource="{Binding TheIListOfObjects}"
... you should manipulate the TheIListOfObjects collection:
TheIListOfObjects = GetNewCollectionItems();
If you have correctly implemented the INotifyPropertyChanged interface in your view model, then your view should update as expected.