C# Online Compiler | .NET Fiddle

using System;
using System.Threading;
using System.Threading.Tasks;
					
public class Program
{
	public static void Main()
	{
		//ParallelLoopStateBreak();
		ParallelLoopStateStop();
	}
	
	private static void ParallelLoopStateBreak() 
	{
		var rnd = new Random();
		int breakIndex = rnd.Next(1, 10);
		
		Parallel.For(1, 100, (i, state) => {
			Console.WriteLine("Beginning iteration {0}", i);
			
			int delay;
			lock(rnd)
			{
				delay = rnd.Next(1, 1000);
			}
			Thread.Sleep(delay);
			
			if(i == breakIndex) 
			{
				Console.WriteLine("Break in iteration {0}", i);
				state.Break();
				return;
			}
			
			if(state.ShouldExitCurrentIteration)
			{
				if(i > state.LowestBreakIteration)
					return;
			}
			Console.WriteLine("Completed iteration {0}", i);
		});
	}
	
	private static void ParallelLoopStateStop() 
	{
		var rnd = new Random();
		int stopIndex = rnd.Next(1, 10);
		
		Parallel.For(1, 100, (i, state) => {
			Console.WriteLine("Beginning iteration {0}", i);
			
			int delay;
			Monitor.Enter(rnd);
			delay = rnd.Next(1, 1000);
			Monitor.Exit(rnd);
			Thread.Sleep(delay);
			
			if(i == stopIndex) 
			{
				Console.WriteLine("Stop in iteration {0}", i);
				state.Stop();
				return;
			}
			
			if(state.IsStopped)
			{
				return;
			}
			Console.WriteLine("Completed iteration {0}", i);
		});
	}
}

 
using System;
using System.Threading;
using System.Threading.Tasks;
                    
public class Program
{
    public static void Main()
    {
        //ParallelLoopStateBreak();
        ParallelLoopStateStop();
    }
    
    private static void ParallelLoopStateBreak() 
    {
        var rnd = new Random();
        int breakIndex = rnd.Next(1, 10);
        
        Parallel.For(1, 100, (i, state) => {
            Console.WriteLine("Beginning iteration {0}", i);
            
            int delay;
            lock(rnd)
            {
                delay = rnd.Next(1, 1000);