Walleby/Wallet.Avalonia/CreateCommentEntryView.axaml

<SettingsExpanderItem
    x:Class="Wallet.Avalonia.CreateCommentEntryView"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="using:Wallet"
    x:DataType="vm:CreateCommentEntryViewModel">
    <SettingsExpanderItem.Resources>
        <ControlTheme x:Key="TextBoxAddButtonStyle" TargetType="Button">
            <Setter Property="Foreground" Value="{DynamicResource TextControlButtonForeground}" />
            <Setter Property="Background" Value="Transparent" />
            <Setter Property="BorderBrush" Value="{DynamicResource TextControlButtonBorderBrush}" />
            <Setter Property="BorderThickness" Value="0" />
            <Setter Property="Template">
                <ControlTemplate>
                    <Border
                        Name="ButtonLayoutGrid"
                        Margin="{DynamicResource TextBoxInnerButtonMargin}"
                        Background="Transparent"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        CornerRadius="{TemplateBinding CornerRadius}">
                        <SymbolIcon
                            Name="Glyph"
                            HorizontalAlignment="Center"
                            VerticalAlignment="Center"
                            FontSize="{StaticResource TextBoxIconFontSize}"
                            Foreground="{TemplateBinding Foreground}"
                            Symbol="Add" />
                    </Border>
                </ControlTemplate>
            </Setter>
            <Style Selector="^:pointerover">
                <Style Selector="^ /template/ Border#ButtonLayoutGrid">
                    <Setter Property="Background" Value="{DynamicResource TextControlButtonBackgroundPointerOver}" />
                    <Setter Property="BorderBrush" Value="{DynamicResource TextControlButtonBorderBrushPointerOver}" />
                </Style>

                <Style Selector="^ /template/ SymbolIcon#Glyph">
                    <Setter Property="Foreground" Value="{DynamicResource TextControlButtonForegroundPointerOver}" />
                </Style>
            </Style>

            <Style Selector="^:pressed">
                <Style Selector="^ /template/ Border#ButtonLayoutGrid">
                    <Setter Property="Background" Value="{DynamicResource TextControlButtonBackgroundPressed}" />
                    <Setter Property="BorderBrush" Value="{DynamicResource TextControlButtonBorderBrushPressed}" />
                </Style>

                <Style Selector="^ /template/ SymbolIcon#Glyph">
                    <Setter Property="Foreground" Value="{DynamicResource TextControlButtonForegroundPressed}" />
                </Style>
            </Style>

            <Style Selector="^:disabled /template/ Border#ButtonLayoutGrid">
                <Setter Property="Opacity" Value="0" />
            </Style>
        </ControlTheme>

    </SettingsExpanderItem.Resources>
    <TextBox
        MaxHeight="216"
        AcceptsReturn="True"
        Text="{Binding Value}"
        TextWrapping="Wrap"
        Watermark="Add a note">
        <TextBox.InnerRightContent>
            <Button
                Width="30"
                Padding="{StaticResource HelperButtonThemePadding}"
                VerticalAlignment="Stretch"
                Command="{Binding InvokeCommand}"
                Content="Add"
                CornerRadius="{DynamicResource ControlCornerRadius}"
                Focusable="False"
                IsTabStop="False"
                Theme="{StaticResource TextBoxAddButtonStyle}" />
        </TextBox.InnerRightContent>
    </TextBox>
</SettingsExpanderItem>