using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Xml.Linq;

using System.Xml;

​

namespace ConsoleApplication1

{

    public class Program

    {

​

        public static void Main(string[] args)

        {    

            //since you do not have values for your array, i populate it will random numbers

            int []yourArray = new int[1000];

            Random r = new Random();

            for (int i = 0; i < yourArray.Length; i++)

                   yourArray[i] = r.Next(10);

            //start the sum function here

            int sum = 0;

            for(int i=0; i < yourArray.Length; i++)

            {

                sum += yourArray[i];

                if(sum >=  500)

                {

                    break;

                }

            }

            Console.WriteLine("Sum : {0}", sum);

        }

    }

}