title: converting to string return null
body: <p>while am trying to convert the return value of add method to string it is not returning any value in console.while i remove the tostring method it is returning value.if i write any character inside the double quote it is showing in console.
  what is happening while am calling tostring method?
  if i didn't put any double quote as parameter it is showing compile time error like (specify culture of string)
  what is the purpose of specifying culture while converting int to string?
  i think i can convert integer value to string by calling tostring method,why can't i do conversion in this scenario?</p>
  
  <pre><code>        private static int Add(int x,int y)
          {
              return x+y;
          }
          static void Main(string[] args)
          {
              Console.WriteLine(Add(23,54).ToString(""));
              Console.ReadKey();
          }
  </code></pre>
  
  <p>thanks.</p>