c# - How we redirect the Page to MainPage.xaml -

i need redirect mainpage.xaml loginpage in silverlight application .i use following ways,

((loginpage)app.current.rootvisual).contentframe.navigate(new uri("/showqueue", urikind.relative));  navigationservice.navigate(new uri("/mainpage", urikind.relative)); 

but didnt achieve?its getting error.

1.code in app.xaml.cs file:

grid rootvisual = new grid();          public void gotopage(usercontrol nextpage)          {              app app = (app)application.current;              app.rootvisual.children.clear();              app.rootvisual.children.add(nextpage);          }           private void application_startup(object sender, startupeventargs e)          {              this.rootvisual = rootvisual;              rootvisual.children.add(new loginpage());           } 

then call gotopage(new mainpage()) in login page. or using navigationservice.navigate(new uri("mainpage.xaml", urikind.relative));