不在运行时生成的控件

再会。在研究 Stillman 和 Green 的书时，出现了一个问题：启动程序时没有错误，但是当按下按钮时，并没有生成敌人并将其放置在比赛场地上。

XAML 代码：

 <Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="Save_The_Humans" Height="700" Width="1000">
    <Window.Resources>
        <ControlTemplate x:Key="EmptyTemplate" TargetType="{x:Type ContentControl}">
            <Grid Height="120" RenderTransformOrigin="0.5,0.5" Width="120" HorizontalAlignment="Center" VerticalAlignment="Center">
                <Grid.RenderTransform>
                    <TransformGroup>
                        <ScaleTransform ScaleX="-1"/>
                        <SkewTransform/>
                        <RotateTransform/>
                        <TranslateTransform/>
                    </TransformGroup>
                </Grid.RenderTransform>
                <Ellipse Fill="#FFFB0606" Stroke="Black" Width="90" Height="90" Margin="13,10,17,20" VerticalAlignment="Stretch"/>
            </Grid>
        </ControlTemplate>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="1"/>
            <RowDefinition/>
            <RowDefinition Height="150"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="140"/>
            <ColumnDefinition/>
            <ColumnDefinition Width="160"/>
        </Grid.ColumnDefinitions>
        <Canvas x:Name="playArea" Grid.Row="1" Grid.ColumnSpan="3" >
            <Canvas.Background>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="Black" Offset="0"/>
                    <GradientStop Color="#FF00FFD1" Offset="1"/>
                </LinearGradientBrush>
            </Canvas.Background>
            <StackPanel x:Name="human" Canvas.Left="430" Orientation="Vertical" Canvas.Top="184" Width="100">
                <Ellipse Fill="White" Height="10" Width="10"/>
                <Rectangle Fill="White" Height="25" Width="10"/>
            </StackPanel>
            <TextBlock x:Name="gameOverText" TextWrapping="Wrap" Text="GAME OVER" FontSize="100" FontFamily="Arial Black" Canvas.Left="175" Canvas.Top="274" FontStyle="Italic" FontWeight="Bold"/>
            <Rectangle Height="50" Width="50" Canvas.Left="640" Canvas.Top="119" RadiusY="10" RadiusX="10" RenderTransformOrigin="0.5,0.5">
                <Rectangle.RenderTransform>
                    <TransformGroup>
                        <ScaleTransform/>
                        <SkewTransform/>
                        <RotateTransform Angle="45"/>
                        <TranslateTransform/>
                    </TransformGroup>
                </Rectangle.RenderTransform>
                <Rectangle.Fill>
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                        <GradientStop Color="#FFDCFF00" Offset="0.359"/>
                        <GradientStop Color="#FFFF00F3" Offset="1"/>
                    </LinearGradientBrush>
                </Rectangle.Fill>
            </Rectangle>
        </Canvas>
        <ProgressBar Grid.Column="1" Grid.Row="2" Height="20"/>
        <ContentControl Content="ContentControl" Grid.Column="2" HorizontalAlignment="Left" Margin="10,30,0,0" Grid.Row="2" VerticalAlignment="Top" Template="{DynamicResource EmptyTemplate}" Height="100" Width="100"/>
        <Button x:Name="button" Content="Button" HorizontalAlignment="Left" Height="100" VerticalAlignment="Top" Width="75" Margin="30,30,0,0" Grid.Row="2" Click="button_Click_1"/>
    </Grid>
</Window>

代码隐藏：

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.Media.Animation;
namespace WpfApplication1
{
    /// <summary>
    /// Логика взаимодействия для MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }   

        Random random = new Random();
        private void button_Click_1(object sender, RoutedEventArgs e)
        {

            AddEnemy();
        }

        private void AddEnemy()
        {
            ContentControl enemy = new ContentControl();
            enemy.Template = Resources["EnemyTemplate"] as ControlTemplate;
            AnimateEnemy(enemy, 0, playArea.ActualWidth - 100, "(Canvas.Left)");
            AnimateEnemy(enemy, random.Next((int)playArea.ActualHeight - 100),
               random.Next((int)playArea.ActualHeight - 100), "(Canvas.Top)");
            playArea.Children.Add(enemy);

        }

        private void AnimateEnemy(ContentControl enemy, double from, double to, string propertyToAnimate)
        {
            Storyboard storyboard = new Storyboard()
            {
                AutoReverse = true,
                RepeatBehavior = RepeatBehavior.Forever
            };
            DoubleAnimation doubleanimation = new DoubleAnimation()
            {
                From = from,
                To = to,
                Duration = new Duration(TimeSpan.FromSeconds(random.Next(4, 6)))
            };
            Storyboard.SetTarget(doubleanimation, enemy);
            Storyboard.SetTargetProperty(doubleanimation, new PropertyPath(propertyToAnimate));
            storyboard.Children.Add(doubleanimation);
            storyboard.Begin();
        }
    }
    }