How to associate a command provided by the DXDocking library with a button

The DXDocking library provides a set of commands on dock panels. These are declared in the DockControllerCommand class. For instance, the Close command allows you to close a specific dock panel. The Activate command activates a dock panel.
This example shows how to associate the Close command with a button. When an end-user clicks the button, the active dock panel is closed.