如何创建可以包含子活动的活动设计器?

您需要将WorkflowItemPresenter控件添加到活动设计器中。

假设您有这样的活动:

[Designer(typeof(MyCompositeDesigner))]
public class MyComposite : NativeActivity
{
    public Activity Body { get; set; }

    protected override void Execute(NativeActivityContext context)
    {
        context.ScheduleActivity(Body);
    }
}

<sap:ActivityDesigner x:Class="WorkflowConsoleApplication3.MyCompositeDesigner"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sap="clr-namespace:System.Activities.Presentation;assembly=System.Activities.Presentation">
    <StackPanel>
        <TextBlock Text="Activity to execute:" 
                   Margin="6"/>
        <sap:WorkflowItemPresenter Item="{Binding Path=ModelItem.Body, Mode=TwoWay}" 
                                   HintText="Drop Activity" 
                 />
    </StackPanel>
</sap:ActivityDesigner>