How to ADD item to listview from textbox.

<Grid>
        <Grid.RowDefinitions>
            <RowDefinition></RowDefinition>
            <RowDefinition></RowDefinition>
        </Grid.RowDefinitions>
        <ListView Grid.Row="0" ItemsSource="{Binding ItemList}"></ListView>
        <StackPanel Grid.Row="1">
            <TextBox BorderThickness="1" HorizontalAlignment="Left" Width="200" Text="{Binding InputPhnText, Mode=TwoWay}"/>
            <Button HorizontalAlignment="Right" Width="100" Command="{Binding InsertCommand}" Content="Add New Items"/>
        </StackPanel>
    </Grid>

public MainWindow()
      {
          InitializeComponent();
          DataContext = new MainViewModel();
      }

public class MainViewModel : INotifyPropertyChanged
    {
        public MainViewModel()
        {
            ItemList = new ObservableCollection<string>() { "9999999999" } ;
            InsertCommand = new RelayCommand(OnInsert);
        }

        private void OnInsert(object obj)
        {
// when you click on button this will hit on your view model and add the phn number.
            if (!string.IsNullOrEmpty(InputPhnText))
            {
                ItemList.Add(InputPhnText);
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public ICommand InsertCommand { get; set; }

        public string InputPhnText{ get; set; }


        public void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public ObservableCollection<string> ItemList { get; set; }

    }

    public class RelayCommand : ICommand
    {
        private Action<object> execute;
        private Func<object, bool> canExecute;

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
        {
            this.execute = execute;
            this.canExecute = canExecute;
        }

        public bool CanExecute(object parameter)
        {
            return this.canExecute == null || this.canExecute(parameter);
        }

        public void Execute(object parameter)
        {
            this.execute(parameter);
        }
    }