xamarin.forms changing property of observablecollection does not update UI - xamarin.forms

Question

I have an observrable collection in my class that contains checkboxes. I implemented a button to check all checkboxes at once. I tried just cycling through all elements and checking the box via binding:
void selectAll_clicked(System.Object sender, System.EventArgs e)
{
var x = sender as Button;
if (!allSelected)
{
allSelected = true;
x.Text = AppResources.DeselectAll;
foreach (var elem in contactList)
elem.isChecked = true;
}
else
{
allSelected = false;
x.Text = AppResources.SelectAll;
foreach (var elem in contactList)
elem.isChecked = false;
}
}
}
I am sure this effects the list, but the UI isnt updated at all.
How can I make sure the observablecollection "updates" visibly?
I also tried adding propertychanged handler:
private void SetList()
{
listview_contacts.ItemsSource = contactList;
contactList.CollectionChanged += items_CollectionChanged;
}
static void items_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.OldItems != null)
{
foreach (INotifyPropertyChanged item in e.OldItems)
item.PropertyChanged -= item_PropertyChanged;
}
if (e.NewItems != null)
{
foreach (INotifyPropertyChanged item in e.NewItems)
item.PropertyChanged += item_PropertyChanged;
}
}
static void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
}
BUt this just says that the cast isnt valid...
Thank you

Answer 1

I was able to achieve that by altering my type like so:
public class ContactType : INotifyPropertyChanged
{
private string _name;
private bool _isChecked;
public string name
{
get => _name; set
{
_name = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(name)));
}
}
public string phone { get; set; }
public string initials { get; set; }
public bool isChecked
{
get => _isChecked; set
{
_isChecked = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(isChecked)));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}