Question

In my mvvm ViewModel I have such field

public int Delta { get; private set; }

However when I update it like that:

Delta = newValue;

UI is not refreshed.

I was thinking that databinding will do that for me. For example I can declare collection as ObservableCollection and then databinding will work.

However there are no ObservableInt, how to say View that it need to be refreshed then?

Probably I should raise some event “notify property changed” or something?

Answer 1

You have two choices:

1. Implement the INotifyPropertyChanged interface on your class.
2. Inherit from DependencyObject and implement Delta as a DependencyProperty.

The simplest option is #1. You can implement the INotifyPropertyChanged interface on your class quite easily:

public class YourClass : INotifyPropertyChanged
{

  private int _delta;
  public int Delta
  {
      get { return _delta; }
      set { _delta = value; PropertyChanged?.Invoke(nameof(Delta)); }
  }

  public event PropertyChangedEventHandler PropertyChanged;
}

You can read more about using and implementing dependency properties on MSDN.