public class Framework_StringConcatVsStringBuilder
{
   [Params(1, 2, 3, 4, 5, 10, 15, 20)]
   public int Loops;

   [Benchmark]
   public string StringConcat()
   {
      string result = string.Empty;
      for (int i = 0; i < Loops; ++i)
           result = string.Concat(result, i.ToString());
      return result;
   }
}