IsNumeric.cs

      public static bool IsNumeric(this string str)
      {
         decimal dec;
         bool numeric = decimal.TryParse(str, out dec);
         if (!numeric)
         {
            // this will handle scientific notation (e.g., "314e-2")
            numeric = decimal.TryParse(str, System.Globalization.NumberStyles.Float, null, out dec);
         }
         return numeric;
      }