How can I access control of parent window from child page in WPF?

Question

I have a window "w" with several controls and a frame "f". I use pages "p1, p2, .." to replace "f". I want to access controls of "w" from "p1". How can I do that?

"w.xaml":

<Window x:Class="WpfApplication.w">
    <Grid>
        <TextBox x:Name="textBox_1" />
        <Frame x:Name="mainFrame" />
    </Grid>
</window>

"p1.xaml":

<Page x:Class="WpfApplication.p1">
    <Grid>
        <Button x:Name="button_1"
            Click="Button_Click" />
    </Grid>

"p1.xaml.cs":

private void Button_Click_Upload(object sender, RoutedEventArgs e)
{
    //set text of textBox_1
}

Answer 1

You can do

private void Button_Click_Upload(object sender, RoutedEventArgs e)
{
    ((w)App.Current.MainWindow).textBox_1.Text = "Your Text";
    //or 
    ((w)Window.GetWindow(this)).textBox_1.Text = "Your Text";
}