Pivot_SelectionChanged中的SDK 7.1和SDK 8.0冲突

我正在尝试为不同的数据透视项实现ApplicationBar的更改。

定义数据透视类型时出现以下错误。

The type 'Microsoft.Phone.Controls.Pivot' exists in both 'c:'Program Files (x86)'Microsoft SDKs'Windows Phone'v7.1'Libraries'Silverlight'Microsoft.Phone.Controls.dll' and 'c:'Program Files (x86)'Reference Assemblies'Microsoft'Framework'WindowsPhone'v8.0'Microsoft.Phone.dll'  D:'projects'MyProject'MyProject'MainPage.xaml.cs

我也使用AppBarUtils进行内部化，不确定这是否取决于这个库

private void Pivot_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    switch ((sender as Pivot).SelectedIndex)
    {
        case 0:
            ApplicationBar = ((ApplicationBar)Application.Current.Resources["AppBar1"]);
            break;
        case 1:
            ApplicationBar = ((ApplicationBar)Application.Current.Resources["AppBar2"]);
            break;
    }
}