using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

using System.Windows.Forms;

​

// YOU CANNOT RUN THIS CODE ONLINE

namespace WindowsFormsApp1

{

    public partial class Form1 : Form

    {

​

        int Calc()

        {

            Thread.Sleep(3000);

            return 42;

        }

​

        // async methods should always return a Task or Task<T> (Task is equivalent to void and Task<int> to int)

        async Task<int> CalcAsync()

        {

            // async method awaits task

            return await Task.Run(() => Calc());

        }

​

        public Form1() { InitializeComponent(); }

​

        private void button1_Click(object sender, EventArgs e)

        {

            // save context to invoke a method later on

            var context = SynchronizationContext.Current;

            var t = new Thread(() =>

            {

                int i = 0;

                while (true)

                {

                    i++;

                    Thread.Sleep(10);

                    // invoke method in UI context

                    context.Send(x => label1.Text = i.ToString(), null);

                    // Invoke() does the same as the syncronization context, but you don't have to save a context (and it only works with winforms)

                    //label1.Invoke( new Action( () => label1.Text = i.ToString() ) );

                }

            });

            // t needs to be a background Thread. This way it automatically stops, when the application is closed.

            t.IsBackground = true;

            t.Start();

        }

​

        // async method

        private async void button2_Click(object sender, EventArgs e)

        {

            button2.Enabled = false;

​

            // async method awaits other async method

            int result = await CalcAsync();

​

            // after await other variables can be accessed

            label2.Text = result.ToString();

​

            button2.Enabled = true;

        }

    }

}

​