Here few useful aliases and mixins:

alias SolidColorBrush(key, color) 
{
  SolidColorBrush Key=$key
  {
    Color: $color
  }
}

alias Thickness(key, left, top, right, bottom) 
{
  Thickness Key=$key
  {
    Left: $left
    Top: $top
    Right: $right
    Bottom: $bottom
  }
}

mixin Size(width=none, height=none) for FrameworkElement
{
  Width: $width
  Height: $height