A C# IsNumeric function, written as an extension method.

NumberFunctions.cs

using System;
using System.Globalization;

namespace NumberFunctionUtilities
{
   public static class NumberFunctions
   {
      public static bool IsNumeric(this object expression)
      {
         if (expression == null)
	 {
	    return false;
	 }
	 double number;
	 return Double.TryParse(Convert.ToString(expression, CultureInfo.InvariantCulture), NumberStyles.Any, NumberFormatInfo.InvariantInfo, out number);
      }
   }
}