如何解决这个XAML错误？

我发现我没有关闭页面，尝试关闭时仍然会出现错误。我想不出问题出在哪里，这可能是因为我对c语言缺乏经验，因为我刚从本周开始学习

请参阅下面的代码，谢谢您的帮助

<Page
x:Class="DrawProg.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:DrawProg"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<common:LayoutAwarePage.Resources>
    <Style x:Key="BaseStatusStyle" TargetType="TextBlock">
        <Setter Property="FontFamily" Value="Segoe UI Semilight"/>
        <Setter Property="FontSize" Value="14.667"/>
        <Setter Property="Margin" Value="0,0,0,5"/>
    </Style>
    <Style x:Key="StatusStyle" BasedOn="{StaticResource BaseStatusStyle}" TargetType="TextBlock">
        <Setter Property="Foreground" Value="Green"/>
    </Style>
    <Style x:Key="ErrorStyle" BasedOn="{StaticResource BaseStatusStyle}" TargetType="TextBlock">
        <Setter Property="Foreground" Value="Blue"/>
    </Style>
</common:LayoutAwarePage.Resources>

<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">

    <Grid x:Name="ContentRoot" Background="{StaticResource ApplicationPageBackgroundThemeBrush}" Margin="100,20,100,20">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <!-- Header -->
        <StackPanel Orientation="Horizontal" Grid.Row="0">
            <Image x:Name="WindowsLogo" Stretch="None" Source="Assets/windows-sdk.png" AutomationProperties.Name="Windows Logo" HorizontalAlignment="Left" Grid.Column="0"/>
            <TextBlock  Text="Windows SDK Samples" VerticalAlignment="Bottom" Style="{StaticResource TitleTextStyle}" TextWrapping="Wrap" Grid.Column="1"/>
        </StackPanel>
        <ScrollViewer x:Name="MainScrollViewer" Grid.Row="1" ZoomMode="Disabled" IsTabStop="False" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" Padding="0,0,0,20" >
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto"/>
                    <RowDefinition Height="*"/>
                </Grid.RowDefinitions>
                <TextBlock x:Name="FeatureName" Grid.Row="0"  Text="Add Sample Title Here" Style="{StaticResource HeaderTextStyle}" TextWrapping="Wrap"/>

                <!-- Content -->
                <Grid Grid.Row="1">

                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="*"/>
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>
                        <TextBlock Grid.Row="0" Text="Input" Style="{StaticResource H2Style}"/>

                        <TextBlock x:Name="ScenarioListLabel" Text="Select Scenario:" Grid.Row="1"  Style="{StaticResource SubheaderTextStyle}" Margin="0,5,0,0" />
                        <ListBox x:Name="Scenarios" Margin="0,0,20,0" Grid.Row="2" AutomationProperties.Name="Scenarios" HorizontalAlignment="Left" 
                                     VerticalAlignment="Top" ScrollViewer.HorizontalScrollBarVisibility="Auto"
                                     AutomationProperties.LabeledBy="{Binding ElementName=ScenarioListLabel}" MaxHeight="125" Padding="0,0,27,0">
                            <ListBox.ItemTemplate>
                                <DataTemplate>
                                    <TextBlock Text="{Binding Name}"/>
                                </DataTemplate>
                            </ListBox.ItemTemplate>
                        </ListBox>
                        <TextBlock x:Name="DescriptionText" Margin="0,5,0,0" Text="Description:" Style="{StaticResource SubheaderTextStyle}" Grid.Row="1" Grid.Column="1"/>

                        <!-- Input Scenarios -->
                        <UserControl x:Name="InputSection" Margin="0,5,0,0" IsTabStop="False" Grid.Row="2" Grid.Column="1" HorizontalAlignment="Left" VerticalAlignment="Top"/>

                        <!-- Output section -->
                        <TextBlock Text="Output" Grid.Row="5"  Margin="0,25,0,20" Style="{StaticResource H2Style}" Grid.ColumnSpan="2"/>
                        <TextBlock x:Name="StatusBlock" Grid.Row="6" Margin="0,0,0,5" Grid.ColumnSpan="2" Visibility="Collapsed"/>

                        <!-- Output Scenarios -->
                        <UserControl x:Name="OutputSection" Grid.Row="7" Grid.ColumnSpan="2" BorderThickness="0"/>
                    </Grid>
                </Grid>
            </Grid>
        </ScrollViewer>

        <!-- Footer -->
        <Grid x:Name="Footer"  Grid.Row="3" Margin="0,10,0,10" VerticalAlignment="Bottom" >
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>

            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Image Grid.Row="0"  Source="Assets/microsoft-sdk.png" AutomationProperties.Name="Microsoft Logo" Stretch="None" HorizontalAlignment="Left"/>
            <TextBlock Style="{StaticResource FooterStyle}" Text="© Microsoft Corporation. All rights reserved." TextWrapping="Wrap" Grid.Row="1" HorizontalAlignment="Left"/>
            <StackPanel x:Name="FooterPanel" Orientation="Horizontal" Grid.Row="1" Grid.Column="1" HorizontalAlignment="Right">
                <HyperlinkButton Content="Terms of use" Tag="http://www.microsoft.com/About/Legal/EN/US/IntellectualProperty/Copyright/default.aspx"
                    Click="Footer_Click" FontSize="12" Style="{StaticResource HyperlinkStyle}"/>
                <TextBlock Text="|" Style="{StaticResource SeparatorStyle}" VerticalAlignment="Center"/>
                <HyperlinkButton Content="Trademarks" Tag="http://www.microsoft.com/About/Legal/EN/US/IntellectualProperty/Trademarks/EN-US.aspx"
                    Click="Footer_Click" FontSize="12" Style="{StaticResource HyperlinkStyle}"/>
                <TextBlock Text="|"  Style="{StaticResource SeparatorStyle}" VerticalAlignment="Center"/>
                <HyperlinkButton Content="Privacy Statement" Tag="http://privacy.microsoft.com" Click="Footer_Click" FontSize="12" Style="{StaticResource HyperlinkStyle}"/>
            </StackPanel>
        </Grid>


    </Grid>

    <VisualStateManager.VisualStateGroups>
        <!-- Visual states reflect the application's window size -->
        <VisualStateGroup>
            <VisualState x:Name="DefaultLayout">
                <Storyboard>
                </Storyboard>
            </VisualState>

            <VisualState x:Name="Below768Layout">
                <Storyboard>

                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Margin)" Storyboard.TargetName="ContentRoot">
                        <DiscreteObjectKeyFrame KeyTime="0">
                            <DiscreteObjectKeyFrame.Value>
                                <Thickness>20,20,20,20</Thickness>
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>
                    </ObjectAnimationUsingKeyFrames>

                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.HorizontalAlignment)" Storyboard.TargetName="FooterPanel">
                        <DiscreteObjectKeyFrame KeyTime="0">
                            <DiscreteObjectKeyFrame.Value>
                                <HorizontalAlignment>Left</HorizontalAlignment>
                            </DiscreteObjectKeyFrame.Value>
                        </DiscreteObjectKeyFrame>
                    </ObjectAnimationUsingKeyFrames>

                </Storyboard>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
</Grid>
</common:LayoutAwarePage>

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尝试用替换最后一个标记

</Page>

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谢谢，我在那之后写了一行，想知道为什么不被接受。我真丢脸：