write string to textblock on different page in C#, UWP

Question

How can I write into a TextBlock on a different page?
So far it only works with TextBlocks on the same page.
The async function is in Page_1 . The TextBlock is on Page_2 .

public async void Serial() 
{
   string rxBuffer;
   //code
   //code
   //code

   while (true)
   {
      textblock_DebugRx_Gas_live.Text = rxBuffer;    
   } 
} 

Answer 1

write string to textblock on different page in C#, UWP

If the two page display in foreground at same time like following.

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="1*"/>
        <RowDefinition Height="1*"/>
    </Grid.RowDefinitions>
    <StackPanel Margin="0,20,0,0" HorizontalAlignment="Center">
        <Button Click="Button_Click" Content="Click" />
        <TextBlock x:Name="Tbk" />
    </StackPanel>

    <Frame Grid.Row="1" VerticalAlignment="Center">
        <local:TestPage />
    </Frame>
</Grid>

You could use Messenger to send message from original page to target page.

using GalaSoft.MvvmLight.Messaging;

private void Button_Click(object sender, RoutedEventArgs e)
{
    var message = "Test";
    Messenger.Default.Send<string,TestPage>(message);
    Tbk.Text = message;
}

Target Page

public TestPage()
{
    this.InitializeComponent();
    this.Loaded += TestPage_Loaded;
}

private void TestPage_Loaded(object sender, RoutedEventArgs e)
{
    Messenger.Default.Register<string>(this, (s) =>
    {
        MyTextBlock.Text = s;
    });
} 

Answer 2

Usually, pages are displayed one at a time, so if you want to pass data between them during navigation, you should do so using the second parameter of the Frame.Navigate method:

this.Frame.Navigate(typeof(SecondPage), someString);

However, an even better solution is to use some kind of MVVM framework, which has a navigation service based on ViewModels, which have a longer lifetime than the UI controls/page. Frameworks like MvvvmCross, MvvmLight, SimpleMvvm or Reactive UI can all help you write such logic in an easier manner.

In your case, you could store the updated state in a view model, which would then be shared by both pages, so any change would be reflected in both places. Instead of directly writing into the Text property of the TextBlocks , you would implement a view model with a string property, which would trigger PropertyChanged event from the INotifyPropertyChanged interface. The MVVM pattern is well described in many tutorials so I encourage you to dig into it.