suggested alternatives.
Windows.xaml
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ed="http://schemas.microsoft.com/expression/2010/drawing"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" x:Class="SpellCheck.MainWindow" x:Name="Window"
Title="MainWindow" Width="400" Height="300">
<Grid Height="300" Width="400">
<Grid.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="White"/>
<GradientStop Color="#FF151518" Offset="0.778"/>
</LinearGradientBrush>
</Grid.Background>
<TextBlock FontSize="14" FontWeight="Bold" Text="A spell-checking TextBox:" Height="28" VerticalAlignment="Top" Margin="19,17,194,0" Foreground="#FF0D0C0E">
<TextBlock.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF121112" Offset="0.896"/>
<GradientStop Color="#FFF1EAE7" Offset="0.478"/>
</LinearGradientBrush>
</TextBlock.Background>
</TextBlock>
<TextBox Margin="19,53,26,85" TextWrapping="Wrap" SpellCheck.IsEnabled="True" Foreground="Black" Text="The qick red focks jumped over the lasy brown dog." BorderThickness="2" BorderBrush="#FF161312" FontSize="12" >
<TextBox.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="White" Offset="0"/>
<GradientStop Color="White" Offset="1"/>
</LinearGradientBrush>
</TextBox.Background>
</TextBox>
</Grid>
</Window>