问为什么这个简单的WPF命令不能工作？

EN

<Window x:Class="H.I.S.windows.CommandTest"
        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:H.I.S.windows"
        mc:Ignorable="d"
        Title="CommandTest" Height="450" Width="800">
    <Window.CommandBindings>
        <CommandBinding Command="local:CustomCommand.Save" CanExecute ="SaveCommand_CanExecute"  Executed="SaveCommand_Executed" />
    </Window.CommandBindings>
    <Grid>
        <Button Command="local:CustomCommand.Save" Height="50" Width="100">Click me!</Button>
    </Grid>
</Window>

namespace H.I.S.windows
{

    public partial class CommandTest : Window
    {
        public CommandTest()
        {
            InitializeComponent();
        }
        private void SaveCommand_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        private void SaveCommand_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            MessageBox.Show("Saved");
        }
    }
    public static class CustomCommand
    {
        public static readonly RoutedUICommand Save = new RoutedUICommand(
            "Save",
            "Save",
            typeof(CustomCommand),
            new InputGestureCollection()
                {
                    new KeyGesture(Key.F2)
                }
            );
    }
}