内部控件模板不显示按钮内容

Question

我用两个按钮创建了一个网格，为第一个按钮创建了一个内部模板；和第二个资源中的按钮模板。 问题是我不明白为什么内部模板不显示按钮的内容？

<Window x:Class="WpfTest.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:WpfTest"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <ControlTemplate x:Key="ButtonTemplate" TargetType="Button">
            <Border BorderBrush="Orange" BorderThickness="3" CornerRadius="2" Background="Red" TextBlock.Foreground="White">
                <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}"/>
            </Border>
        </ControlTemplate>
    </Window.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Button Grid.Column="0" Content="Button_A" >
            <Button.Template>
                <ControlTemplate >
                    <Border BorderBrush="Orange" BorderThickness="3" CornerRadius="2" Background="Red" TextBlock.Foreground="White">
                        <ContentPresenter ContentSource="Content" HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}"/>
                    </Border>
                </ControlTemplate>
            </Button.Template>
        </Button>
        <Button Grid.Column="1" Content="Button_B" Template="{StaticResource ButtonTemplate}">
        </Button>
    </Grid>
</Window>