Mahapps.Metro :在 MetroWindow 类型中找不到可附加属性 WindowCommand

我以为我会使用Mahapps.Metro尝试一些WPF Metro，但遇到了错误：

在 MetroWindow 类型中找不到可附加属性 WindowCommand。

我已经包含了来自 nuget 的包，并具有以下 xaml：

<Controls:MetroWindow x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colours.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Window.Resources>
    <Controls:MetroWindow.WindowCommands>
        <Controls:WindowCommands>
            <Button Content="settings" />
        </Controls:WindowCommands>
    </Controls:MetroWindow.WindowCommands>

    <Controls:MetroContentControl>
        <Button Content="Blah" Height="20" Width="150" />
    </Controls:MetroContentControl>
</Controls:MetroWindow>

和背后的代码：

using MahApps.Metro.Controls;
namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : MetroWindow 
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }
}

我正在尝试获取类似于此处文档中的标题栏。

有什么想法吗？