工作流基础：相同域下的自托管工作流

Question

如何在一个Workflowhost中加载多个工作流（操作）？

这不起作用：

System.ServiceModel.Activities.WorkflowService wf = XamlServices.Load("service.xaml") as System.ServiceModel.Activities.WorkflowService;
WorkflowServiceHost workflowServiceHost = new WorkflowServiceHost(wf,new Uri("http://localhost:123/service"));
workflowServiceHost.Open();

wf = XamlServices.Load("service2.xaml") as System.ServiceModel.Activities.WorkflowService;
WorkflowServiceHost workflowServiceHost = new WorkflowServiceHost(wf,new Uri("http://localhost:123/service"));
workflowServiceHost.Open();

我只能得到一个例外，该URL已经被使用。我加载的xaml文件由Receive和SendReply操作组成。我想在同一个域下进行多项操作。