Unfortunately, WPF lacks a simple Split Button control. Basically, it is the regular button usually used to consolidate a set of variations of a command, especially when one of the commands is used most of the time.
Typical (expanded) split button might look like this one shown from Outlook 2007:
In this recipe we will create a really simple but effective split button with accompanying drop-down menu.
Start your Expression Blend 4 and then select New project... From the dialog that appears select WPF and then WPF Application, make sure that Language is set to C# and Version is 4.0. At the end ...