WF从加载和卸载访问工作流实例变量

In workflowRuntime_WorkflowUnloaded and Loaded etc.. the only thing I can get which is pretty useless is the workflowinstanceId. I want to be able to access some DPs that are on the root activity, whenever I do a GetWorkFlowDefintion() and cast to root activity, all the property that I've passed in are all null.. In workflowRuntime_WorkflowUnloaded and Loaded