I have read and review all of this but still the only way to use Esri styles and brushes is through DynamicResources. I can't find nothing in SDK where I would be able to do this but with Esri Brushes
TextBlock descrip = new TextBlock()
{
Visibility = Windows.Visibility.Visible,
TextWrapping = TextWrapping.Wrap,
TextTrimming = TextTrimming.CharacterEllipsis,
Background = Media.Brushes.Black
};