1、xaml页面

<Window x:Class="EssentialWPF.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Title="MainWindow" Height="350" Width="525">

    <Grid>

        <Button

            Name="_button1"

            HorizontalAlignment="Center"

            VerticalAlignment="Center"

            FontSize="9pt">

            Hello World

        </Button>

    </Grid>

</Window>

2、后台

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.Windows.Threading;

namespace EssentialWPF

{

    /// <summary>

    /// MainWindow.xaml 的交互逻辑

    /// </summary>

    public partial class MainWindow : Window

    {

        long _start;

        public MainWindow()

        {

            InitializeComponent();

            DispatcherTimer timer = new DispatcherTimer();

            timer.Interval = TimeSpan.FromMilliseconds(50);

            _start = Environment.TickCount;

            timer.Tick += timer_Tick;

            timer.IsEnabled = true;

        }

        void timer_Tick(object sender, EventArgs e)

        {

            long elapsed = Environment.TickCount - _start;

            if (elapsed >= 5000)

            {

                _button1.FontSize = 18.0;

                ((DispatcherTimer)sender).IsEnabled = false;

                return;

            }

            _button1.FontSize = 9.0 + (9.0 / (5000.0 / elapsed));

        }

    }

}