WPF DispatcherTimer(定时器应用) 无人触摸60s自动关闭窗口

如果无人触摸：60s自动关闭窗口

xmal:部分

<s:SurfaceWindow x:Class="SurfaceApplication1.SurfaceWindow1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:s="http://schemas.microsoft.com/surface/2008"
    Title="SurfaceApplication1"
                 TouchDown="SurfaceWindow_TouchDown"
    >
    <Grid  >
        <Button Width="80" Height="80" Background="Yellow" Click="Button_Click">OK</Button>
        <Label x:Name="lblSeconds"> 你好！</Label>
    </Grid>
</s:SurfaceWindow>

cs:部分

//60s无人操作自动关闭
        DispatcherTimer dTimer;
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            //构造一个DispatcherTimer类实例
            dTimer = new System.Windows.Threading.DispatcherTimer();
            //设置事件处理函数
            dTimer.Tick += new EventHandler(dispatcherTimer_Tick);
        }
        private void dispatcherTimer_Tick(object sender, EventArgs e)
        {
            this.Close();
        }

　　　//触摸后重新给“i”赋值
        private void SurfaceWindow_TouchDown(object sender, TouchEventArgs e)
        {
            int i = 60;
            //定时器时间间隔1s
            if ( dTimer.Interval!=null)
            {
                dTimer.Interval = new TimeSpan(0, 0, i);
                dTimer.Start();
            }
        }