C# dotnet Create a factorial program that returns an error indication when something goes wrong

  class MyMathFunctions  
   {  
     public const int NEGATIVE_NUMBER = -1;  
     public const int NON_INTEGER_VALUE = -2;  
     public static double Factorial(double value)  
     {  
       if (value < 0)  
       {  
         return NEGATIVE_NUMBER;  
       }  
       int valueAsInt = (int)value;  
       if (valueAsInt != value)  
       {  
         return NON_INTEGER_VALUE;  
       }  
       double factorial = 1.0;  
       do  
       {  
         factorial *= value;  
         value -= 1.0;  
       } while (value > 1);  
       return factorial;  
     }  
   }  
   public class Program1  
   {  
     public static void Main(string[] args)  
     {  
       for (int i = 6; i > -6; i--)  
       {  
         double factorial = MyMathFunctions.Factorial(i);  
         if (factorial == MyMathFunctions.NEGATIVE_NUMBER)  
         {  
           Console.WriteLine("Factorial() passed a negative number");  
           break;  
         }  
         if (factorial == MyMathFunctions.NON_INTEGER_VALUE)  
         {  
           Console.WriteLine("Factorial() passed a non-integer number");  
           break;  
         }  
         Console.WriteLine("i = {0}, factorial = {1}", i, factorial);  
         Console.ReadLine();  
       }  
     }  
   }