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CSharp · Console

/Program.cs

using System;
using System.Threading.Tasks;
using System.Threading;

public class Program
{

	public static void Main()
	{		
		AutoResetEvent waitA = new AutoResetEvent(false);
		AutoResetEvent waitB = new AutoResetEvent(false);
		
		// Start tasks
		Task task_1 = Task.Run(() =>
									   {
										   Console.WriteLine("1");
										   waitA.Set();
										   waitB.WaitOne();
										   Console.WriteLine("3");
									   });
		
		Task task_2 = Task.Run(() =>
									   {
										   waitA.WaitOne();
										   Console.WriteLine("2");
										   waitB.Set();
									   });
		task_2.Wait();
	}
}