ObservableCollection is not updated

Question

I have this code

It is my PersonModel PersonModel.cs

public class PersonModel
{
   List<Person> list = new List<Person>();

   #region Constructors       
   public PersonModel()
   {

   }       
   #endregion Constructors)

   #region Methods       
   public List<Person> GetPersons()
   {

       list.Add(new Person("Иванов", "Иван", "Иванович", new DateTime(1980, 5, 10), Gender.Male));
       list.Add(new Person("Петр", "Петрович", "Петров", new DateTime(1977, 9, 21), Gender.Male));
       list.Add(new Person("Виктория", "Викторовна", "Викторова", new DateTime(1991, 1, 7), Gender.Female));

       return list;       
   }

   public List<Person> SetPersons()
   {
       list.Add(new Person("Маташков", "Сергей", "Сергеевич", new DateTime(1980, 5, 10), Gender.Male));
       return list;      
   }      
   #endregion Methods       
}

It is my PersonViewModel PersonsViewModel.cs

public class PersonsViewModel<TViewType> : INotifyPropertyChanged, IViewModel where TViewType : IView, new()
{
   private readonly IView _view;
   private readonly PersonModel _model;

   public ObservableCollection<Person> Persons { get; set; }
   public RelayCommand OkCommand { get; private set; }

   private string _str;

   public PersonsViewModel()
   {
       this._view = new TViewType();
       this._model = new PersonModel();
       this.Persons = new ObservableCollection<Person>(this._model.GetPersons());
       this.OkCommand = new RelayCommand(o => this.OKRun());

       _str = "Кнопка";       

       this._view.SetDataContext(this);
       this._view.ShowView();            
   }

   public string Str
   {
       get { return _str; }
       set
       {
           if (_str == value)
               return;
           _str = value;
           OnPropertyChanged("Str");     
       }
   }

   public ObservableCollection<Person> Observ
   {
       get { return Persons; }
       set
       {
           if (Persons == value)
               return;
           Persons = value;
           OnPropertyChanged("Observ");     
       }
   }

   public event PropertyChangedEventHandler PropertyChanged;

   //[NotifyPropertyChangedInvocator]
   protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
   {
       var handler = PropertyChanged;
       if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
   }       

   private void OKRun()
   {
       Str = "Refresh";
       this.Persons = new ObservableCollection<Person>(this._model.SetPersons());
   }
}

It is my PersonsView

PersonsView.xaml

<DataGrid ItemsSource="{Binding Observ, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" />

I want updated Datadrid?

Why do not updated Datagrid and observablecollection?

Answer 1

In your constructor you should write :

this.Observ= new ObservableCollection<Person>(this._model.SetPersons());

Instead of

this.Persons = new ObservableCollection(this._model.SetPersons());