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How to implement a timer with .NETCoreApp1.0 or .NETCoreApp1.1

For a .NET Core project, I needed to implement a timer to execute some tasks at regular intervals.

Before ASP.NET Core, I used to use the System.Timers DLL, which provides everything I needed to implement the timer I wanted, something like this:

public class Class1
{
    Timer tm = null;

    public Class1()
    {
        this.tm.Elapsed += new ElapsedEventHandler(Timer_Elapsed);
        this.tm.AutoReset = true;
        this.tm = new Timer(60000);
    }

    protected void Timer_Elapsed(object sender, ElapsedEventArgs e)
    {
         this.tm.Stop();

         try
         {
             // My business logic here
         }
         catch (Exception)
         {
             throw;
         }
         finally
         {
             this.tm.Start();
         }
     }
}

With ASP.NET Core, you can't use System.Timers anymore; you have to use the System.Threading.Timer package, which provides almost the same things.

This is a quick example of a timer implemented with this package:

namespace ConsoleApp
{
    using System;
    using System.Threading;

    public class Program
    {
        Timer _tm = null;

        AutoResetEvent _autoEvent = null;

        private int _counter = 0;

        public static void Main(string[] args)
        {
            Program p = new Program();
            p.StartTimer();
        }

        public void StartTimer()
        {
            _autoEvent = new AutoResetEvent(false);
            _tm = new Timer(Execute, _autoEvent, 1000, 1000);
            Console.Read();
        }

        public void Execute(Object stateInfo)
        {
            if (_counter < 10)
            {
                Console.WriteLine("Call #" + _counter);
                _counter++;
                return;
            }

            Console.WriteLine("Final call");
            _tm.Dispose();
        }
    }
}

If, after adding the System.Threading.Timer package to your project, your project doesn't build anymore, it's because you have to add a dependency to the Microsoft.NETCore.App platform type in your .NET Core framework:

{
  "version": "1.0.0-*",
  "buildOptions": {
    "emitEntryPoint": true
  },

  "dependencies": {
    "Microsoft.NETCore.App": "1.1.0" // REMOVE THIS LINE
    "System.Threading.Timer": "4.3.0"
  },

  "frameworks": {
    "netcoreapp1.1": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.1.0"
        }
      },
      "imports": "dnxcore50"
    }
  }
}

Note that if you add the dependency to the netcoreapp framework, you have to remove the first dependency line to the .NET Core framework, otherwise you will get the error: An item with the same key has already been added. Key: Microsoft.NETCore.App