Volatile

2 Threads sync the variable, e.g. Thread 1 set true, the true value will bring to Thread 2.

if without volatile , the step 3 will not run, and stop in while loop. (Run in Release Mode)

 private volatile bool _loop = true;

 static void Main(string[] args)

 {

     Program test1 = new Program();

     Thread obj = new Thread(SomeThread);

     obj.Start(test1);

     Thread.Sleep(200);

     test1._loop = false;

     Console.WriteLine("Step 2 : Value is set to False");

 }

 private static void SomeThread(object o1)

 {

     Program o = (Program)o1;

     Console.WriteLine("Step 1 - Enter Loop");

     while (o._loop)

     {

     }

     Console.WriteLine("Step 3 - Exit Loop");

 }