/// <summary>
 /// 级联绑定菜单
 /// </summary>
 /// <param name="item"></param>
 private Task OnCascadeBindSelectClick(SelectedItem item)
 {
     Items2.Clear();
     if (item.Value == "Beijing")
     {
         Items2.AddRange(new SelectedItem[]
         {
             new SelectedItem("1", "朝阳区")
             {
                 Active = true
             },
             new SelectedItem("2", "海淀区")
         });
     }
     else if (item.Value == "Shanghai")
     {
         Items2.AddRange(new SelectedItem[]
         {
             new SelectedItem("1", "静安区"),
             new SelectedItem("2", "黄浦区")
             {
                 Active = true
             },
         });
     }
     Select1.SetItems(Items2);
     return(Task.CompletedTask);
 }