How to move or swap two GridView items?

<Page
    x:Class="GridViewItemSwap.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:GridViewItemSwap"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <GridView x:Name="gridview" IsItemClickEnabled="True" ItemClick="gridview_ItemClick" >
            <GridView.ItemTemplate >
                <DataTemplate >
                    <Border Margin="12" Width="100" Height="100" Background="Blue" >
                        <TextBlock Text="{Binding}"/>
                    </Border>
                </DataTemplate>
            </GridView.ItemTemplate>
        </GridView>
    </Grid>
</Page>

namespace GridViewItemSwap
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        private int? firstvalue;
        private ObservableCollection<Int32> data = new ObservableCollection<int>();
        public MainPage()
        {
            this.InitializeComponent();
            for(int i =0 ; i <4; i++)
            {
                data.Add(i);
            }
            gridview.ItemsSource = data;
        }

        private void gridview_ItemClick(object sender, ItemClickEventArgs e)
        {
           if (firstvalue.HasValue )
           {
               Int32 secondvalue = (Int32)e.ClickedItem;
               var firstindex= data.IndexOf(firstvalue.Value);
               var secondindex = data.IndexOf(secondvalue);
               data[firstindex] = secondvalue;
               data[secondindex] = firstvalue.Value ;
               firstvalue = null;

           }
           else
           {
               firstvalue = (Int32)e.ClickedItem; 
           }

        }
    }
}

---

在現實生活中，你和誰在一起的確很重要，甚至能改變你的成長軌跡，決定你的人生成敗。 和什麼樣的人在一起，就會有什麼樣的人生。 和勤奮的人在一起，你不會懶惰； 和積極的人在一起，你不會消沈； 與智者同行，你會不同凡響； 與高人為伍，你能登上巔峰。