BaseViewModel

gistfile1.cs

public class BaseViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged([CallerMemberName]string propertyName = "") =>
       PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    protected void SetValue<T>(ref T backingField, T value, [CallerMemberName]string propertyName = null)
    {
        if (EqualityComparer<T>.Default.Equals(backingField, value))
            return;
        backingField = value;
        OnPropertyChanged(propertyName);
    }
}

// set properties like this in child view models
private string _someProperty;
public string SomeProperty
{
    get { return _someProperty; }
    set { SetValue(ref _someProperty, value); }
}