<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>