Не обновляется содержимое по нажатию кнопки

При нажатии кнопки должен добавляться вопрос, но этого не происходит
Код окна:

namespace TestSuit
{
    /// <summary>
    /// Логика взаимодействия для Constructor.xaml
    /// </summary>
    public partial class Constructor : Window, INotifyPropertyChanged
    {
        private int countQuestions = 0;
        public ObservableCollection<CQuestion> Questions = new();
        public ObservableCollection<CAnswer> Answers { get; set; }
        public event PropertyChangedEventHandler PropertyChanged;
        public ObservableCollection<CQuestion> MyCollection { get; set; }
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
        public Constructor()
        {
            InitializeComponent();
            DataContext = this;
            Answers = new();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Answers.Add(new CAnswer("Ответ"));
            Questions.Add(new CQuestion
            {
                Text = "Вопрос",
                CAnswers = Answers
            });
            MyCollection = Questions;
            OnPropertyChanged();
            Answers.Clear();
            countQuestions++;
        }

        private void AddAnswer_Click(object sender, RoutedEventArgs e)
        {

        }
    }

    public class CQuestion
    {
        public string Text { get; set; }
        public ObservableCollection<CAnswer> CAnswers { get; set; }
    }

    public class CAnswer
    {
        public CAnswer(string Text)
        {
            this.Text = Text;
        }
        public string Text { get; set; }
        public bool Selected { get; set; }
        public bool IsTrue { get; set; }
    }
}

Разметка окна:

<Window x:Class="TestSuit.Constructor"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:TestSuit"
        mc:Ignorable="d"
        Title="Constructor" Height="450" Width="800">
    <ScrollViewer>
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="205*"/>
                <ColumnDefinition Width="600*"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>
            <ItemsControl x:Name="ControlMain" ItemsSource="{Binding MyCollection}" Margin="5,5,5,5" Grid.ColumnSpan="2">
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <StackPanel>
                            <TextBox Text="{Binding Text}" FontWeight="Bold"/>
                            <ItemsControl ItemsSource="{Binding CAnswers}" Margin="5">
                                <ItemsControl.ItemTemplate>
                                    <DataTemplate>
                                        <RadioButton GroupName="{Binding DataContext.Text, RelativeSource={RelativeSource AncestorType=ItemsControl, AncestorLevel=1}}" 
                                                 Content="{Binding Text}" 
                                                 IsChecked="{Binding Selected}"
                                                 Margin="5"/>
                                    </DataTemplate>
                                </ItemsControl.ItemTemplate>
                                <Button x:Name="AddAnswer" Content="Добавить ответ" Click="AddAnswer_Click"/>
                            </ItemsControl>
                        </StackPanel>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
            <Button x:Name="AddQuestion" Content="Добавить вопрос" Grid.Row="1" Margin="5,5,5,5" Click="Button_Click" Grid.ColumnSpan="2"/>
        </Grid>
    </ScrollViewer>
</Window>