Question

I got the error on var ts = System.Threading.ThreadStart(delegate() (Red line has drown under System.Threading.ThreadStart). What is the problem?

using System;
using System.Threading;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        public Program()
        {
            int[] iArray = new int[3];
            iArray[0] = 2;
            iArray[1] = 1;
            iArray[2] = 5;
            var ts = System.Threading.ThreadStart(delegate()
            {
                foreach (int i in iArray)
                    Foo(i);
            });
        }

        public void Foo(int i)
        {
            Console.WriteLine(i + ",");
        }

        public static void Main(String[] args)
        {
            Program p = new Program();
        }
    }
}

Answer 1

You are missing a new:

var ts = new System.Threading.ThreadStart(delegate()
         {
             foreach (int i in iArray)
                 Foo(i);
         });

BTW:

You don’t have to prefix ThreadStart with its namespace System.Threading, because you already have a using declaration for it at the top of your *.cs file.