notepad/NotePad/MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="NotePad.MainWindow"
        Title="Untitled - Notepad"
        Width="600" Height="400">

    <Window.Styles>
        <Style Selector="Menu">
            <Setter Property="Background" Value="#D3D3D3"/>
        </Style>
        <Style Selector="MenuItem">
            <Setter Property="Background" Value="#D3D3D3"/>
            <Setter Property="Foreground" Value="Black"/>
        </Style>
        <Style Selector="MenuItem:pointerover /template/ Border#PART_LayoutRoot">
            <Setter Property="Background" Value="#A9A9A9"/>
        </Style>
        <Style Selector="MenuItem:open /template/ Popup#PART_Popup > Border">
            <Setter Property="Background" Value="#D3D3D3"/>
            <Setter Property="BorderBrush" Value="#A9A9A9"/>
            <Setter Property="BorderThickness" Value="1"/>
        </Style>
        <Style Selector="Separator">
            <Setter Property="Background" Value="#A9A9A9"/>
        </Style>
    </Window.Styles>

    <DockPanel>
        <!-- Menu Bar -->
        <Menu DockPanel.Dock="Top">
            <MenuItem Header="_File">
                <MenuItem Header="_New" Click="OnNewClick" InputGesture="Ctrl+N"/>
                <MenuItem Header="_Open..." Click="OnOpenClick" InputGesture="Ctrl+O"/>
                <MenuItem Header="_Save" Click="OnSaveClick" InputGesture="Ctrl+S"/>
                <MenuItem Header="Save _As..." Click="OnSaveAsClick"/>
                <Separator/>
                <MenuItem Header="E_xit" Click="OnExitClick"/>
            </MenuItem>
            <MenuItem Header="_Edit" x:Name="EditMenuItem">
                <MenuItem Header="_Undo" Click="OnUndoClick" InputGesture="Ctrl+Z"/>
                <Separator/>
                <MenuItem Header="Cu_t" Click="OnCutClick" InputGesture="Ctrl+X"/>
                <MenuItem Header="_Copy" Click="OnCopyClick" InputGesture="Ctrl+C"/>
                <MenuItem Header="_Paste" Click="OnPasteClick" InputGesture="Ctrl+V"/>
                <MenuItem Header="De_lete" Click="OnDeleteClick" InputGesture="Delete"/>
                <Separator/>
                <MenuItem Header="Select _All" Click="OnSelectAllClick" InputGesture="Ctrl+A"/>
                <MenuItem Header="Time/_Date" Click="OnTimeDateClick" InputGesture="F5"/>
            </MenuItem>
            <MenuItem Header="F_ormat">
                <MenuItem Header="_Word Wrap" x:Name="WordWrapMenuItem" Click="OnWordWrapToggle">
                    <MenuItem.Icon>
                        <CheckBox x:Name="WordWrapCheckBox" IsChecked="False" IsHitTestVisible="False"/>
                    </MenuItem.Icon>
                </MenuItem>
            </MenuItem>
            <MenuItem Header="_Help">
                <MenuItem Header="_About Notepad" Click="OnAboutClick"/>
            </MenuItem>
        </Menu>

        <!-- Text Editor Area -->
        <Border Background="White" BorderThickness="0">
            <TextBox x:Name="EditorTextBox"
                     AcceptsReturn="True"
                     AcceptsTab="True"
                     TextWrapping="NoWrap"
                     VerticalAlignment="Stretch"
                     HorizontalAlignment="Stretch"
                     ScrollViewer.VerticalScrollBarVisibility="Auto"
                     ScrollViewer.HorizontalScrollBarVisibility="Auto"
                     BorderThickness="0"
                     Background="White"
                     Foreground="Black"
                     CaretBrush="Black"
                     FontFamily="Courier New,Liberation Mono,Courier,monospace"
                     FontSize="13"
                     ClearSelectionOnLostFocus="False">
                <TextBox.Styles>
                    <Style Selector="TextBox">
                        <Setter Property="Background" Value="White"/>
                        <Setter Property="Foreground" Value="Black"/>
                    </Style>
                    <Style Selector="TextBox:pointerover /template/ Border#PART_BorderElement">
                        <Setter Property="Background" Value="White"/>
                        <Setter Property="BorderBrush" Value="Transparent"/>
                    </Style>
                    <Style Selector="TextBox:focus /template/ Border#PART_BorderElement">
                        <Setter Property="Background" Value="White"/>
                        <Setter Property="BorderBrush" Value="Transparent"/>
                    </Style>
                </TextBox.Styles>
            </TextBox>
        </Border>
    </DockPanel>
</Window>