gistfile1.txt

% cat test3.cs
using System;
using System.IO;
using System.Threading;
using System.Collections.Generic;

public class Test {
    private static Timer t1;
    private static Timer t2;
    private static Timer t3;
    public static void Main () {
        t1 = new Timer(Callback1, null, 0, 1000);
        t2 = new Timer(Callback2, null, 0, 1000);
        t3 = new Timer(Callback3, null, 0, 1000);
        Console.ReadLine();
    }

    private static void Callback1(Object o) { Console.Write('1'); }
    private static void Callback2(Object o) { Console.Write('2'); }
    private static void Callback3(Object o) { Console.Write('3'); }
}
% ~/opt/mono-2.6.4/bin/gmcs test3.cs
test3.cs(7,26): warning CS0414: The private field `Test.t1' is assigned but its value is never used
test3.cs(8,26): warning CS0414: The private field `Test.t2' is assigned but its value is never used
test3.cs(9,26): warning CS0414: The private field `Test.t3' is assigned but its value is never used
Compilation succeeded - 3 warning(s)
% ~/opt/mono-2.4/bin/mono test3.exe
213321321321321321321321321321zsh: exit 58    ~/opt/mono-2.4/bin/mono test3.exe
% ~/opt/mono-2.6.4/bin/mono test3.exe
33333333333333333zsh: exit 58    ~/opt/mono-2.6.4/bin/mono test3.exe