/// <summary>
 /// 得到流程模型
 /// </summary>
 /// <returns></returns>
 public Workflow GetWorkflow()
 {
     if (_workflow == null)
         _workflow = this.GetContext().Store.GetWorkflow(this.WorkflowGuid);
     return _workflow;
 }
 /// <summary>
 /// 设置工作流模型
 /// </summary>
 /// <param name="workflow"></param>
 public void SetWorkflow(Workflow workflow)
 {
     this._workflow = workflow;
 }