Setting editor border
WPF HTML editor control has a border:

You can change color and width of this border using properties EditorBorderColor and EditorBorderWidth

C#
private void Window1_OnLoaded(object sender, RoutedEventArgs e)
{
wpfHtmlEditor1.EditorBorderWidth = new Thickness(10);
wpfHtmlEditor1.EditorBorderColor = Color.FromRgb(6, 165, 19);
}VBPrivate Sub Window1_OnLoaded(sender As Object, e As RoutedEventArgs) wpfHtmlEditor1.EditorBorderWidth = New Thickness(10) wpfHtmlEditor1.EditorBorderColor = Color.FromRgb(6, 165, 19) End SubAlso you can completely hide the border. In order to do that you should just set EditorBorderWidth property = new Thickness(0)