WPF Menu and Submenu Styling as Blue Gradient Background

MenuBlueGradient.xaml

<!--Specifies the blue Gradient Background -->
<Menu.Resources>
    <LinearGradientBrush x:Key="MenuBackroundBrush"
                            EndPoint="0,1"
                            StartPoint="0,0">
        <GradientStop Color="#FF3A60AD"
                        Offset="0.528" />
        <GradientStop Color="#FF6A85D8"
                        Offset="0.01" />
        <GradientStop Color="#FF3464C4"
                        Offset="1" />
        <GradientStop Color="#FF202E7E"
                        Offset="1" />
    </LinearGradientBrush>

    <Style TargetType="Menu">
        <Setter Property="Background"
                Value="{StaticResource MenuBackroundBrush}" />
    </Style>

    <Style TargetType="MenuItem">
        <Setter Property="Background"
                Value="{StaticResource MenuBackroundBrush}" />
    </Style>
</Menu.Resources>

MenuDropShadowEffect.xaml

<!-- Elevates the whole menu outside of the gradient work -->
<Menu.BitmapEffect>
    <DropShadowBitmapEffect />
</Menu.BitmapEffect>

MenuItemSubMenusExample.xaml

<!--Example to have submenus bound-->

<MenuItem Header="Recent"
        Foreground="GhostWhite"
        FontSize="16"
        Margin="6"
        ItemsSource="{Binding Path=RecentJsons}"
        Click="SelectMRU"
        FontWeight="Bold">
   <MenuItem.Icon>
       <Image Source="/Assets/history.png" />
   </MenuItem.Icon>
</MenuItem>

MenuItemTemplate.xaml

<!--Handle the gray Popup background for submenus-->
<MenuItem.Template>
    <ControlTemplate TargetType="MenuItem">
        <Border Name="Border">
            <Grid>
                <ContentPresenter Margin="6,3,6,3"
                                    ContentSource="Header"
                                    RecognizesAccessKey="True" />
                <Popup Name="Popup"
                        Placement="Bottom"
                        IsOpen="{TemplateBinding IsSubmenuOpen}"
                        AllowsTransparency="True"
                        Focusable="False"
                        PopupAnimation="Fade">
                    <Border Name="SubmenuBorder"
                            SnapsToDevicePixels="True"
                            Background="LightBlue"
                            BorderBrush="Transparent"
                            BorderThickness="1">
                        <StackPanel IsItemsHost="True"
                                    KeyboardNavigation.DirectionalNavigation="Cycle" />
                    </Border>
                </Popup>
            </Grid>
        </Border>
        <ControlTemplate.Triggers>
            <Trigger Property="IsSuspendingPopupAnimation"
                        Value="true">
                <Setter TargetName="Popup"
                        Property="PopupAnimation"
                        Value="None" />
            </Trigger>
            <Trigger Property="IsHighlighted"
                        Value="true">
                <Setter TargetName="Border"
                        Property="Background"
                        Value="LightBlue" />
                <Setter TargetName="Border"
                        Property="BorderBrush"
                        Value="Transparent" />
                <Setter Property="Foreground"
                        Value="Firebrick" />
            </Trigger>
            <Trigger  Property="IsHighlighted"
                        Value="False">
                <Setter Property="Foreground"
                        Value="Black" />
            </Trigger>
            <Trigger SourceName="Popup"
                        Property="Popup.AllowsTransparency"
                        Value="True">
                <Setter TargetName="SubmenuBorder"
                        Property="CornerRadius"
                        Value="0,0,4,4" />
                <Setter TargetName="SubmenuBorder"
                        Property="Padding"
                        Value="0,0,0,3" />
            </Trigger>
            <Trigger Property="IsEnabled"
                        Value="False">
                <Setter Property="Foreground"
                        Value="DarkGray" />
            </Trigger>
        </ControlTemplate.Triggers>
    </ControlTemplate>
</MenuItem.Template>

MenuItemUsageExample.xaml

<!-- Nothing special for each MenuItem, the below has an image on the left and Orange text -->

<MenuItem Header="Clipboard Load"
            Foreground="Orange"
            FontSize="16"
            Margin="6"
            ToolTip="Load JSON From Clipboard"
            Command="{Binding JSONLoadFromClipboard}"
            FontWeight="Bold">
    <MenuItem.Icon>
        <!-- Remember to make the png file as a `Resource` to the solution, so its embedded in the exe -->
        <Image Source="/Assets/clipboard-arrow-down-outline.png" />
    </MenuItem.Icon>
</MenuItem

MenuTopLevelInstantiation.xaml

<!-- Example Menu top level template. -->
<Menu Height="Auto"
        Name="menu1"
        Grid.ColumnSpan="2"
        Margin="20, 8, 20, 8"
        HorizontalAlignment="Stretch"
        VerticalAlignment="Top"
        Foreground="Transparent"
        FontSize="16"
        FontWeight="Bold"
        BorderThickness="2"
        >
  <!-- Fill in other items within the Gist here -->

</Menu>

MRU.cs

public class MRU
{
    public string Name { get; set; }
    public string Address { get; set; }

    public string Data { get; set; }

    public bool IsValid => !string.IsNullOrWhiteSpace(Name);

    public bool IsFile => !string.IsNullOrWhiteSpace(Address);

    public bool IsData => !IsFile;

    public MRU(string address)
    {
        if (string.IsNullOrWhiteSpace(address)
            || !File.Exists(address))  return;
            
        Address = address;

        Name = System.IO.Path.GetFileName(address);
    }

    public override string ToString() => Name;
}

MRUCodeBehindClick.cs

// Install-Package Ben.Demystifier -Version 0.4.1
// The VM's Error is a notified string. This example
// can use the visual error box (placed hidden at the bottom of the main page until an error is in the error property)
// - Error box example at https://gist.github.com/CheetahChrome/e21884ab06e85e27cb2c950ea0b01c60

private void SelectMRU(object sender, RoutedEventArgs e)
{
    try
    {
        var mru = (e.OriginalSource as MenuItem).DataContext as MRU;

        if (mru is not null)
        {
            VM.ClearAll();

            this.Title = mru.Name;

            ShowJSON(File.ReadAllText(mru.Address));
        }
    }
    catch (Exception ex)
    {
        VM.Error = ex.Demystify().ToString();
    }
}

VM.cs

using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Runtime.CompilerServices;
using System.Text.Json;
using System.Windows.Input;
using Microsoft.Expression.Interactivity.Core;

public class MainVM : INotifiedPropertyChanged
{

private ObservableCollection<MRU> _MRUS;

public ObservableCollection<MRU> MRUS
{
    get { return _MRUS; }
    set { _MRUS = value; OnPropertyChanged(nameof(MRUS)); }
}

// One can optionally use the visual error box (placed hidden at the bottom of the main page until an error is in the error property)
// - Error box example at https://gist.github.com/CheetahChrome/e21884ab06e85e27cb2c950ea0b01c60
private string _Error;

public string Error
{
    get => _Error;
    set { _Error = value; OnPropertyChanged(nameof(Error)); OnPropertyChanged(nameof(HasError)); }
}

public bool HasError => !string.IsNullOrEmpty(Error);


public VM()
{
    MRUS = new ObservableCollection<MRU>(GetMRUS());
}

public List<MRU> GetMRUS()
{
    try
    {
        var mruText = Properties.Settings.Default.MRUS;
        return string.IsNullOrWhiteSpace(mruText) ? new List<MRU>()
            : JsonSerializer.Deserialize<List<MRU>>(mruText);
    }
    catch (Exception ex)
    {
        Error = ex.ToStringDemystified();
    }

    return null;
}

// Add a user `Setting` (in the project properties) of `MRUS` of type `string` as `User` setting.

public void AddMRUToUserSettings(MRU mRU)
{
    try
    {
        MRUS.Add(mRU);
        var asList = MRUS.ToList<MRU>();
        Properties.Settings.Default.MRUS = JsonSerializer.Serialize(asList);
        Properties.Settings.Default.Save();

    }
    catch (Exception ex)
    {
        Error = ex.Demystify().ToString();
    }        
}

        /// <summary>
        /// Event raised when a property changes.
        /// </summary>
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// Raises the PropertyChanged event.
        /// </summary>
        /// <param name="propertyName">The name of the property that has changed.</param>
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = "")
            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    }

This WPF based Gist creates a menu bar with an MRU sub list which is saved to the User Settings by Json serialization which looks like this: