How to update bindings inside DataTemplate? - wpf

Question

Let's say I have the following ListView in my view
<ListView x:Name="ListView1" ItemsSource="{Binding SomeCollection}">
<ListView.ContextMenu>
<ContextMenu>
<MenuItem Header="Do something" Command="{Binding SomeCommand, Mode=OneWay}" />
</ContextMenu>
</ListView.ContextMenu>
<ListView.ItemTemplate>
<DataTemplate DataType="model:Person">
<StackLayout>
<TextBlock Text="{Binding Name}">
<Image Source="{Binding State, Converter={StaticResource StateToIconConverter}, Mode=OneWay}" />
</StackLayout>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Now, this Person is a model and its properties do not have any way to inform the view of them being updated (according to MVVC). But, I need to update the view after SomeCommand gets executed, because items inside SomeCollection get edited.
I tried doing this
public void ExecuteSomeCommand() {
// change the state of some person inside SomeCollection
(ListView1.SelectedItems[0] as Person).State = "Some different state";
// now inform the view of change, so it can reflect in the DataTemplate
ListView1.GetBindingExpression(ListBox.ItemsSourceProperty).UpdateTarget();
}
And I thought this would propagate into the DataTemplate, but it doesn't. Is there any other way to do this? How should I change my approach?

Answer 1

When the model used in data binding implements the INotifyPropertyChanged Interface the UI is automatically updated when you modify a property of the model.
public class Person : INotifyPropertyChanged
{
private Image _state;
public Image State
{
get => _state;
set {
if (value != _state) {
_state = value;
OnPropertyChanged(nameof(State));
}
}
}
// ... other properties here ...
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}