得到一个工作流当前结点里面的可用选项

string s = txtGuid.Text.Trim();
        if(s.Length>0)
        {
            Guid instanceId = new Guid(s);
            StateMachineWorkflowInstance stateInstance = new StateMachineWorkflowInstance(Application[MyWorkHelpr.WorkflowRuntimeName] as WorkflowRuntime, instanceId);
            using(DataTable dt = new DataTable())
            {
                dt.Columns.Add("NID",typeof(string));
                dt.Columns.Add("NTEXT",typeof(string));
                dt.Rows.Add("-1","==请选择==");
                int i=0;
                foreach(Activity act in stateInstance.CurrentState.EnabledActivities)
                {
                    if (act is EventDrivenActivity )
                    {
                        EventDrivenActivity edact = (EventDrivenActivity)act;
                        if (edact.EnabledActivities.Count >0 && edact.EnabledActivities[0] is HandleExternalEventActivity)
                        {
                            dt.Rows.Add(edact.Name, act.Description);
                        }
                    }
                    i++;
                }
                DropDownList1.DataValueField = "NID";
                DropDownList1.DataTextField = "NTEXT";
                DropDownList1.DataSource = dt;
                DropDownList1.DataBind();