title: How to add or subtract very large numbers without bigint in C#?
body: <p>So let me start by saying that I'm a newbie with little to moderate knowledge about C#.</p>
  
  <p>Coming to the topic: I need to make a program that is able to add/subtract very large integers. Initially, used BigInt only to find out it's not allowed. There should be a logical workaround for this? I have an idea which is using "elementary school method" where you add each digit starting from right to left.</p>
  
  <p>I made a string which I split into char array and added each digit from right to left(GetUpperBound-i). But it doesn't seem to work.</p>
  
  <p>My Code:</p>
  
  <pre><code>string s, s2;
  char[] c_arr, c_arr2;
  int i, erg;
  
  s = "1234";
  s2 = "5678";
  c_arr = s.ToCharArray();
  c_arr2 = s2.ToCharArray();
  for (i = 0; i &lt;= c_arr.GetUpperBound(0); i++)
  {
      erg = c_arr[c_arr.GetUpperBound(0)-i]+c_arr2[c_arr2.GetUpperBound(0)-i];
      Console.Write(erg);
  }
  
  Console.ReadKey();
  </code></pre>