错误：
错误 1 Event handler 'LongListSelector_SelectionChanged' not found on class 'welcome.MainPage'
<phone:PhoneApplicationPage
x:Class="welcome.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DataContext="{d:DesignData SampleData/MainViewModelSampleData.xaml}"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
shell:SystemTray.IsVisible="False">
<Grid x:Name="LayoutRoot" Background="Transparent">
<phone:Panorama Title="Time Machine" FontFamily="Segoe WP Black">
<phone:Panorama.Background>
<ImageBrush ImageSource="/welcome;component/Assets/BGP.png"/>
</phone:Panorama.Background>
<phone:PanoramaItem Header=" LOOK!" FontWeight="Bold" FontStyle="Italic" FontFamily="Andy" FontSize="24">
<StackPanel Margin="0,-6,0,12">
<TextBlock Text="Time is ELAPSEING......" FontSize="48"/>
</StackPanel>
</phone:PanoramaItem>
<phone:PanoramaItem>
<phone:LongListSelector Margin="0,-38,-22,2" ItemsSource="{Binding Items}" SelectionChanged="LongListSelector_SelectionChanged">
<phone:LongListSelector.ListHeaderTemplate>
<DataTemplate>
<Grid Margin="12,0,0,38">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Text=" HEARD!"
Style="{StaticResource PanoramaItemHeaderTextStyle}"
Grid.Row="0" FontWeight="Bold" FontStyle="Italic"/>