using System;

using System.Threading;

using System.Threading.Tasks;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        AccessForLoopVariables();

        AccessForEachVariables();

        PassCustomData();

    }

    private static void AccessForLoopVariables()

    {

        Task[] taskArray = new Task[10];

        for(int i = 0; i < 10; i++) 

        {

             taskArray[i] = Task.Factory.StartNew(() => Console.WriteLine($"Data: {i}"));

        }

        Task.WaitAll(taskArray);

    }

    private static void AccessForEachVariables()

    {

        List<Task> tasks = new List<Task>();

        string[] urls = Enumerable.Range(1, 10).Select(x => "Url-" + x.ToString()).ToArray();

        foreach(var url in urls)

        {

             tasks.Add(Task.Factory.StartNew(() => Console.WriteLine($"Data: {url}")));

        }

        Task.WaitAll(tasks.ToArray());

    }

    private static void PassCustomData()

    {

        Task[] taskArray = new Task[10];

        for(int i = 0; i < 10; i++) 

        {

             taskArray[i] = Task.Factory.StartNew((Object obj) => {

                    var data = obj as CustomData;

                    data.ThreadId = Thread.CurrentThread.ManagedThreadId;

                }, new CustomData { Index = i});

        }

        Task.WaitAll(taskArray);

        foreach (var task in taskArray) 

        {

            var data = task.AsyncState as CustomData;

            Console.WriteLine($"ThreadId {data.ThreadId} Index: {data.Index}");

        }

    }

}

​

class CustomData

{

   public int Index;

   public int ThreadId;

}