#180 – How Layout Works

Layout in WPF is the process by which a container (e.g. Grid, StackPanel) arranges its child elements (e.g. Button, Label).  The container figures out the final size and position of each child element, which dictates how the container’s children will be rendered.

The layout process is triggered when a container is first being rendered or when a property on a child control changes (if that property can affect layout).

Layout is basically a conversation between the container and its children.  This conversation consists of two phases:

• Measure – Container asks each child what its desired size is
• Arrange – Container figures out how to arrange its children and decides on final position and size of each child

How a container arranges its children is dependent on the specific class.  E.g. A Grid puts its children in rows and columns, while a StackPanel stacks children horizontally or vertically.