问使用绑定创建的菜单与使用MaterialDesignThemes包创建的菜单不同

EN

xaml

<Window x:Class="EvoLogger.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:Logger" 
        xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
        mc:Ignorable="d"
        WindowStyle="None"      
        AllowsTransparency="True"
        BorderThickness="1"
        ResizeMode ="CanResizeWithGrip"
        MouseLeftButtonDown="Window_MouseLeftButtonDown"
        Title="MainWindow" Height="800" Width="800">

    <Grid Margin="0,5,0,5">
        <Grid.RowDefinitions>
            <RowDefinition Height="40"/>
            <RowDefinition Height="40"/>
            <RowDefinition Height="40"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Menu Grid.Row="1" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" ItemsSource="{Binding MenuItems}">
            <Menu.ItemContainerStyle>
                <Style TargetType="{x:Type MenuItem}">
                    <Setter Property="Command" Value="{Binding Command}" />
                </Style>
            </Menu.ItemContainerStyle>
            <Menu.ItemTemplate>
                <HierarchicalDataTemplate DataType="{x:Type local:MenuItemViewModel}" ItemsSource="{Binding Path=MenuItems}">
                    <TextBlock Text="{Binding Header}"/>
                </HierarchicalDataTemplate>
            </Menu.ItemTemplate>
        </Menu>
        
        <Menu x:Name="mainMenu" IsMainMenu="True" Grid.Row="2">
            <Menu.ItemsPanel>
                <ItemsPanelTemplate>
                    <StackPanel HorizontalAlignment="Stretch" Orientation="Horizontal"/>
                </ItemsPanelTemplate>
            </Menu.ItemsPanel>
            <MenuItem Header="_File" Height="40">
                <MenuItem
                            Header="Save"
                            Icon="{materialDesign:PackIcon Kind=ContentSave}">
                </MenuItem>

                <MenuItem Header="Save As.."/>

                <MenuItem
                            Header="Exit"
                            InputGestureText="Ctrl+E"
                            Icon="{materialDesign:PackIcon Kind=ExitToApp}"/>

                <Separator/>

                <MenuItem
                            Header="Excellent"
                            IsCheckable="True"
                            IsChecked="True"/>

                <MenuItem
                            Header="Rubbish"
                            IsCheckable="True"/>

                <MenuItem
                            Header="Dig Deeper"
                            InputGestureText="Ctrl+D">
                    <MenuItem
                                Header="Enlightenment?"
                                IsCheckable="True"/>
                    <MenuItem
                                Header="Disappointment"
                                IsCheckable="True"/>
                </MenuItem>

                <MenuItem
                            Header="Look Deeper"
                            InputGestureText="Ctrl+D">
                    <MenuItem Header="Plain"/>
                    <MenuItem Header="Ice Cream"/>
                </MenuItem>
            </MenuItem>

            <MenuItem Header="_Edit" Height="40">
                <MenuItem
                            Header="_Cut"
                            Command="Cut"
                            Icon="{materialDesign:PackIcon Kind=ContentCut}"/>

                <MenuItem
                            Header="_Copy"
                            Command="Copy"
                            Icon="{materialDesign:PackIcon Kind=ContentCopy}"/>

                <MenuItem
                            Header="_Paste"
                            Command="Paste"
                            Icon="{materialDesign:PackIcon Kind=Cog}"/>
            </MenuItem>
        </Menu>
    </Grid>
</Window>


cs
using System;
using System.Windows;
using EvoConfiguration;
using System.IO;
using System.Windows.Input;
using System.Collections.ObjectModel;

namespace Logger
{
    public partial class MainWindow : Window
    {
        public ObservableCollection<MenuItemViewModel> MenuItems { get; set; }

        public MainWindow()
        {
            InitializeComponent();

            MenuItems = new ObservableCollection<MenuItemViewModel>
            {
                new MenuItemViewModel { Header = "Alpha" },
                new MenuItemViewModel { Header = "Beta",
                    MenuItems = new ObservableCollection<MenuItemViewModel>
                        {
                            new MenuItemViewModel { Header = "Beta1" },
                            new MenuItemViewModel { Header = "Beta2",
                                MenuItems = new ObservableCollection<MenuItemViewModel>
                                {
                                    new MenuItemViewModel { Header = "Beta1a" },
                                    new MenuItemViewModel { Header = "Beta1b" },
                                    new MenuItemViewModel { Header = "Beta1c" }
                                }
                            },
                            new MenuItemViewModel { Header = "Beta3" }
                        }
                },
                new MenuItemViewModel { Header = "Gamma" }
            };

            DataContext = this;
        }

        

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Window2 w2 = new Window2();

            w2.Show();
        }

        private void Window_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            DragMove();
        }
    }

    public class MenuItemViewModel
    {
        private readonly ICommand _command;

        public MenuItemViewModel()
        {
            _command = new CommandViewModel(Execute);
        }

        public string Header { get; set; }

        public ObservableCollection<MenuItemViewModel> MenuItems { get; set; }

        public ICommand Command
        {
            get
            {
                return _command;
            }
        }

        private void Execute()
        {
            // (NOTE: In a view model, you normally should not use MessageBox.Show()).
            MessageBox.Show("Clicked at " + Header);
        }
    }

    public class CommandViewModel : ICommand
    {
        private readonly Action _action;

        public CommandViewModel(Action action)
        {
            _action = action;
        }

        public void Execute(object o)
        {
            _action();
        }

        public bool CanExecute(object o)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged
        {
            add { }
            remove { }
        }
    }
}