<Application 
    x:Class="WPListDirectoriesAndFiles.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"       
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:system="clr-namespace:System;assembly=mscorlib"
    xmlns:mpc="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:phoneNavigation="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone">
    
    <!--RootFrame points to and loads the first page of your application-->
    <Application.RootVisual>
        <phoneNavigation:PhoneApplicationFrame x:Name="RootFrame" Source="/MainPage.xaml"/>
    </Application.RootVisual>
</Application>