Assuming you also don't want the regular @ key to send 2 depending on Shift state, you could make that key the only UnicodeKey instance in your custom layout, and then create a global UnicodeKey template in Xaml -

<DataTemplate DataType="{x:Type vk:UnicodeKey}">
	<ContentControl HorizontalContentAlignment="Center" VerticalContentAlignment="Center">
		<TextBlock Text="{Binding Character}"/>
	</ContentControl>
</DataTemplate>
 

Otherwise if you only need to use different colors or font for @, it should also be possible to use a data trigger in the template that checks for @ value and applies respective property setters.

Regards,
Slavcho
Mindfusion

You could use KeyboardCreator to add UnicodeKey to your custom layout, setting its Character to @. Load the layout file by calling -

keyboard.TemplateLayout = KeyboardLayout.Create(filePath); 

Add the template to a resource dictionary somewhere in your Xaml -

<Window ...>
	<Window.Resources>
		<DataTemplate DataType="{x:Type vk:UnicodeKey}">
			<ContentControl HorizontalContentAlignment="Center" VerticalContentAlignment="Center">
				<TextBlock Text="{Binding Character}"/>
			</ContentControl>
		</DataTemplate>
	</Window.Resources> 

Regards,
Slavcho
Mindfusion