MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x804 上介绍了“空白页”项模板

namespace CanvasSizeChangedTest
{
    /// <summary>
    /// 可用于自身或导航至 Frame 内部的空白页。
    /// </summary>
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        Random rnd = new Random();

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            RandomSize();
        }

        private void RandomSize()
        {
            InnerCanvas.Width = rnd.Next(1, (int)OuterCanvas.ActualWidth);
            InnerCanvas.Height = rnd.Next(1, (int)OuterCanvas.ActualHeight);
        }

        private void Page_Loaded(object sender, RoutedEventArgs e)
        {
            RandomSize();
        }

        private void InnerCanvas_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            Debug.WriteLine($"Inner Canvas Size Changed: {e.NewSize}");
        }
    }
}