Add Two String Numbers which may be large - Author MC, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Globalization;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
               String s1 = "000123456"; String s2 = "78901234512345";
               Int64 tempResult = 0;
               Int64 remainder = 0;
               int strLen1 = 0;
               int strLen2 = 0;
               string sNum1 = null;
               string sNum2 = null;
               string result = "";
               Int64 nNum1 = 0; Int64 nNum2 = 0;

// while more chunks
               while (s1.Length > 0 || s2.Length > 0)
               { 
                  tempResult = 0;
                  strLen1 = s1.Length < 10 ? s1.Length: 10;
                  strLen2 = s2.Length < 10 ? s2.Length: 10;
                  sNum1 = s1.Substring(s1.Length-strLen1, strLen1);
                  sNum2 = s2.Substring(s2.Length-strLen2, strLen2);
                   Console.Write("NUM1:");
                   Console.WriteLine(sNum1);
                   Console.Write("NUM2:");
                   Console.WriteLine(sNum2);
                  s1 = s1.Substring(0, s1.Length-strLen1);
                  s2 = s2.Substring(0, s2.Length-strLen2);
                   nNum1 = 0; nNum2 =0;
                     try
                     {
                           if (sNum1.Length > 0)
                               nNum1 = Int64.Parse( sNum1, NumberStyles.Number);
                           if (sNum2.Length > 0)
                               nNum2 = Int64.Parse( sNum2, NumberStyles.Number);
                      }
                      catch (FormatException fe)
                      {
                          Console.WriteLine(fe.Message);
                          if (fe.InnerException != null)
                              Console.WriteLine(fe.InnerException.Message);
                          throw new Exception("Part of Number is Invalid :" + (!String.IsNullOrEmpty(sNum1) ? sNum1 : "null"));
                      }
                  
                   
                    
                  tempResult = remainder;
               // convert addition to string
                  Console.Write("nNum1:"); Console.WriteLine(nNum1.ToString());
                  Console.Write("nNum2:"); Console.WriteLine(nNum2.ToString());
                   
                  tempResult = tempResult + nNum1;
                  tempResult = tempResult + nNum2;
                  remainder = tempResult > Int32.MaxValue ? tempResult-Int32.MaxValue : 0;
                  if (tempResult > Int32.MaxValue)
                      tempResult = Int32.MaxValue;
                  Console.Write("TempResult:");  Console.WriteLine(tempResult.ToString());
                  result = tempResult.ToString() + result;
               } 
               Console.Write(" RESULT : " ); Console.WriteLine(result);
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,14 sec, absolute running time: 0,09 sec, cpu time: 0,09 sec, average memory usage: 14 Mb, average nr of threads: 3