TwoWay Data Binding with MVVM Light on Windows Phone 8.1 - xaml

Question

I'm trying to create a custom Button with ListPickerFlyout using MVVM. The result that i wanna reach is something like that:
custom Button with ListPickerFlyout
My problem is how to bind the SelectedItem from ListPickerFlyout to the content TextBlock.
I'm using MVVM Light Windows Phone 8.1 (Store Appp).
My Xaml code:
<Button Background="White"
HorizontalAlignment="Stretch"
HorizontalContentAlignment="Stretch">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="40" />
</Grid.ColumnDefinitions>
<!-- Content TextBlock -->
<TextBlock Text="{Binding MyVM.SelectedItem, Mode=TwoWay}"
Style="{StaticResource DefaultTextBlock}"
FontSize="22"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Margin="10, 0, 0, 0"/>
<Image Height="20" Grid.Column="1"
VerticalAlignment="Center" HorizontalAlignment="Center"
Source="../Assets/icons/arrow_down.png"/>
</Grid>
<Button.Flyout>
<ListPickerFlyout PickerFlyoutBase.Title="$Items$"
ItemsSource="{Binding MyVM.listItems}"
SelectedItem="{Binding MyVM.SelectedItem, Mode=TwoWay}" >
<ListPickerFlyout.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding}"
Style="{StaticResource DefaultTextBlock}"
FontSize="22"/>
</StackPanel>
</DataTemplate>
</ListPickerFlyout.ItemTemplate>
</ListPickerFlyout>
</Button.Flyout>
And in MyVM i have
public string SelectedItem { get; set; }
Edit:
Solved the problem, i forgot to add RaisePropertyChanged("SelectedItem");.
So, in my MVVM class:
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
if (_selectedItem != value)
{
_selectedItem = value;
RaisePropertyChanged("SelectedItem");
}
}
}

Answer 1

Just need to add the RaisePropertyChanged("SelectedItem"); in MVVM class.
The complete code:
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
if (_selectedItem != value)
{
_selectedItem = value;
RaisePropertyChanged("SelectedItem");
}
}
}