missing: type or namespace for DispatcherTimer and RoutedEventArgs

Question

Timer function missing:

type or namespace for

DispatcherTimer and RoutedEventArgs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Alarm
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
void timer_Tick(object sender, EventArgs e)
{
DispatcherTimer timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromSeconds(10);
timer.Tick += timer_Tick;
timer.Start();
}

    private async void button1_Click( object sender, RoutedEventArgs e  )
    {
    MessageBox.Show( "Start timer" );

    await Task.Delay( TimeSpan.FromSeconds(10) );

    MessageBox.Show( "10 seconds later" );
    }
}

}