<SequentialWorkflowActivity x:Class="MyWorkflow" x:Name="MyWorkflow" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/workflow"> <CodeActivity x:Name="codeActivity1" /> <x:Code><![CDATA[ public class Foo : SequentialWorkflowActivity { public Foo() { Console.WriteLine("FOOO!!!!"); } } ]]></x:Code> </SequentialWorkflowActivity>