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>