Simple Blinking Text

Question

I'm trying to put together a simple demo project of blinking "Hello World" text with the least code possible in C#/WPF. What I have written compiles and runs, but does not actually blink the text (it's based off of a timer that fires every 2 seconds and changes the visibility of the label. Any thoughts on why the text isn't blinking or what a more efficient approach would be? Code:

using System;
using System.Timers;
using System.Windows;

namespace BlinkingText
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        static Timer _timer;
        static MainWindow window = new MainWindow();

    public MainWindow()
    {
        InitializeComponent();

        Start();
    }

    public static void Start()
    {
        var timer = new Timer(2000);
        timer.Elapsed += new ElapsedEventHandler(_timer_Elapsed);
        timer.Enabled = true;
        _timer = timer;
    }

    public static void _timer_Elapsed(object sender, ElapsedEventArgs e)
    {

        if (window.HelloWorldLabel.Visibility == Visibility.Hidden)
        {
            Application.Current.Dispatcher.Invoke((Action)delegate
            {
                window.HelloWorldLabel.Visibility = Visibility.Visible;
            });
        }
        else
        {
            Application.Current.Dispatcher.Invoke((Action)delegate
            {
                window.HelloWorldLabel.Visibility = Visibility.Hidden;
            });
      }
    }
  }
}

Answer 1

The text in your application does not blink because you change the Visibility of a Label in a hidden MainWindow instance, which is not identical to the one that you see on screen.

It is created by

static MainWindow window = new MainWindow();

but never shown.

Besides that, you should use a DispatcherTimer like this:

public partial class MainWindow : Window
{
    private readonly DispatcherTimer timer =
        new DispatcherTimer { Interval = TimeSpan.FromSeconds(2) };

    public MainWindow()
    {
        InitializeComponent();

        timer.Tick += Timer_Tick;
        timer.Start();
    }

    private void Timer_Tick(object sender, EventArgs e)
    {
        HelloWorldLabel.Visibility = HelloWorldLabel.Visibility == Visibility.Visible
            ? Visibility.Hidden : Visibility.Visible;
    }
}

---

You may also do something similar entirely in XAML, e.g. like this:

<TextBlock Text="Hello, World.">
    <TextBlock.Triggers>
        <EventTrigger RoutedEvent="Loaded">
            <BeginStoryboard>
                <Storyboard>
                    <ObjectAnimationUsingKeyFrames
                        Storyboard.TargetProperty="Visibility"
                        Duration="0:0:4" RepeatBehavior="Forever">

                        <DiscreteObjectKeyFrame
                            KeyTime="0:0:0"
                            Value="{x:Static Visibility.Visible}"/>
                        <DiscreteObjectKeyFrame
                            KeyTime="0:0:2"
                            Value="{x:Static Visibility.Hidden}"/>
                    </ObjectAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </TextBlock.Triggers>
</TextBlock>