'Usage

Dim instance As CompositeActivity

'Declaration

<ActivityValidatorAttribute(GetType(CompositeActivityValidator))> _
<ContentPropertyAttribute("Activities")> _
<ActivityCodeGeneratorAttribute(GetType(CompositeActivityCodeGenerator))> _
Public Class CompositeActivity _
    Inherits Activity

public class HasOneChildActivity : CompositeActivity
{
    protected override ActivityExecutionStatus Execute(ActivityExecutionContext executionContext)
    {
        Activity child = this.EnabledActivities[0];
        child.Closed += this.ChildClosed;
        executionContext.ExecuteActivity(child);

        return ActivityExecutionStatus.Executing;
    }

    void ChildClosed(object sender, ActivityExecutionStatusChangedEventArgs e)
    {
        e.Activity.Closed -= this.ChildClosed;
        ActivityExecutionContext executionContext = sender as ActivityExecutionContext;

        executionContext.CloseActivity();
    }
}