C# Online Compiler | .NET Fiddle

using System;
using System.Linq;
using System.Threading.Tasks;

public class Program
{
	public static void Main()
	{
		var numbers = Enumerable.Range(0, 10);
		Parallel.ForEach(numbers, i =>
		{
			var vm = VoteMachine.Instance;
			vm.RegisterVote();
		});
		Console.WriteLine(VoteMachine.Instance.TotalVotes);
	}
}

public class VoteMachine
{
	private static readonly Lazy<VoteMachine> _instance = new Lazy<VoteMachine>(() => new VoteMachine());    
	private int _totalVotes = 0;
	

	private VoteMachine()
	{
	}

	public static VoteMachine Instance
	{
		get
		{
			return _instance.Value;
		}
	}

	public void RegisterVote()
	{
		_totalVotes += 1;
		Console.WriteLine("Registered Vote #" + _totalVotes);
	}

	public int TotalVotes
	{
		get
		{
			return _totalVotes;
		}
	}
}

 
using System;
using System.Linq;
using System.Threading.Tasks;
​
public class Program
{
    public static void Main()
    {
        var numbers = Enumerable.Range(0, 10);
        Parallel.ForEach(numbers, i =>
        {
            var vm = VoteMachine.Instance;
            vm.RegisterVote();
        });
        Console.WriteLine(VoteMachine.Instance.TotalVotes);
    }
}
​
public class VoteMachine
{
    private static readonly Lazy<VoteMachine> _instance = new Lazy<VoteMachine>(() => new VoteMachine());    
    private int _totalVotes = 0;
    
​

Cached Result

-126,45 €
8