Timer Speed is increasing on picker selection change - xamarin.forms

Question

I am creating a timer which is working on a picker selection changed.Timer is working good until the times end to the "00:00:00".If i change the selection changed in the mid of time then the speed of timer is increased and if i again change selected index than timer run much fast. My problem is that timer should run on 1 sec dealy every time.
I am sharing my code below. Thanks in advance for help.
//picker selection change
private async void GName_SelectedIndexChanged(object sender, EventArgs e)
{
lblEndTime.Text = "00:00:10";
StartTimmer();
}
public void StartTimmer()
{
Device.StartTimer(TimeSpan.FromSeconds(1), () =>
{
Device.BeginInvokeOnMainThread(() =>
{
TimeSpan timeSpan = TimeSpan.Parse(lblEndTime.Text);
timeSpan -= TimeSpan.FromSeconds(1);
if (lblEndTime.Text == "00:00:00")
{
returnValue = false;
}
else
{
lblEndTime.Text = Convert.ToString(timeSpan);
}
});
return returnValue;
});
}

Answer 1

Use a System.Timer and stop the timer every time you change the selected index instead of creating a new one.
public partial class MainPage : ContentPage
{
Timer Timer1 { get; set; }
public MainPage()
{
InitializeComponent();
}
public void StartTimmer()
{
if (Timer1 != null)
{
Timer1.Stop();
Timer1.Dispose();
}
Timer1 = new Timer();
Timer1.Interval = 1000;
Timer1.Enabled = true;
Timer1.Start();
Timer1.Elapsed += (object sender, System.Timers.ElapsedEventArgs e) =>
{
Device.BeginInvokeOnMainThread(() =>
{
TimeSpan timeSpan = TimeSpan.Parse(lblEndTime.Text);
timeSpan -= TimeSpan.FromSeconds(1);
if (lblEndTime.Text == "00:00:00")
{
Timer1.Stop();
Timer1.Dispose();
}
else
{
lblEndTime.Text = Convert.ToString(timeSpan);
}
});
};
}
private void Button_Clicked(object sender, EventArgs e)
{
lblEndTime.Text = "00:00:10";
StartTimmer();
}
}
And in xaml:
<StackLayout>
<!-- Place new controls here -->
<Label x:Name="lblEndTime" Text="Welcome to Xamarin.Forms!"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
<Button Text="Click Me" Clicked="Button_Clicked"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
</StackLayout>