is there a way bind viewmodel to view with INotifyDataChangedEvent

Question

I am currently trying to make a client-side chat app with C#, so ı am using WPF for UI. But there is a problem, when ı try to bind data to source. view can receive data from viewmodel but just once. I have tried much ways, finally ı think ı have problem in OnPropertyChanged event. But I can't find the trouble.

Here are my codes:

    class ObservableObject: INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChaned([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }

Data from MainViewModel (I implemented this class from ObservableObject Class)

        private string _contactName;
        public string ContactName { get { return _contactName; } set { _contactName = value; OnPropertyChanged(); } }

finally, the xaml code (At the beginning of the xaml code, ı imported the mainviewmodel as datacontext)

                        <TextBlock>
                        <!--name-->
                        <Run
                            Text="{Binding ContactName, UpdateSourceTrigger=PropertyChanged
                            ,FallbackValue='Kişi İsmi', TargetNullValue='Kişi İsmi'}"
                            FontWeight="Bold"
                            FontSize="20"/>
                        <LineBreak/>
                        
                        <!--online status-->
                        <Run 
                            Text="{Binding LastSeen, UpdateSourceTrigger= PropertyChanged}"
                            FontSize="15"/>
                        </TextBlock>

In the above, just an example ı have same problem all of the datas.

When I changed the ContactName from MainViewModel with buttonclick event e.t.c there is nothing happens.

Answer 1

I Found the problem,

while ı'm creating the ObservableObject Class, I did not implement it from INotifyPropetyChanged interface. Then the updated ObservableObject Class must be like that:

class ObservableObject: INotifyPropertyChanged
{
    //Bu sınıf MVVM kalıbımızın ViewModel Katmanının View katmanı tarafından anlaşılabilmesi için, built-in olarak verilen INotifyPropertyChanged interface'ini daha kolay hale getirmiştir.
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChaned([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}