actions and tasks, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

using System.Threading;
using System.Threading.Tasks;//required for tasks / concurrent programming

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string str;
            Action a;
            Task t;
            a = () => Console.WriteLine("Test");
            a +=  delegate { Console.WriteLine("Test2"); };            
            
            str = "testingasync";
            t = RunAsync(str);
        
            t = Task.Factory.StartNew(()=>ShowThreadInfo("abc"));
            a();
        }
       static void ShowThreadInfo(String s)
       {
           Console.WriteLine("{0} Thread ID: {1}", s, Thread.CurrentThread.ManagedThreadId);
       }
        
        private static async Task RunAsync(String s)
        {
            await Task.Run(()=>{Console.WriteLine(s);});
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,14 sec, cpu time: 0,14 sec, average memory usage: 16 Mb, average nr of threads: 4, absolute service time: 0,35 sec