Exception Handling and Weight Conversion

Hey all, So, for my final in C# we have to write a few programs. Some of them being pretty simple. The one I'm doing now asks me to write a weight conversion program with a minimum of grams, ounces, kilograms and pounds. If the user enters a negative number or a letter then it's supposed to throw and handle an exception. Well, everything was going great until I encountered this problem. At the moment, I'm trying to convert grams to kilograms, pounds and ounces. It works great when I'm converting grams to ounces or kilograms, but whenever I want to convert the grams to pounds, it handles an exception and says "Invalid input value.". I have the user select what they want to convert said grams to by inputting a number. The number for pounds is 3, but whenever the user enters 3 to convert to pounds it handles said exception. Here's my code: WeightConverterTest Class using System; using System.Collections.Generic; using System.Text; namespace Final_Question_3 {     class WeightConverterTest     {         static void Main(string[] args)         {             //declare variables             int selection = 0;             while (selection < 5)             {                                 try                 {                     //prompt user to select a measurement type to be converted                     Console.WriteLine("Select measurement type:" +                         "\n1) Grams\t2) Kilograms\t3) Ounces\t4) Pounds\n" +                         "5) Exit the program.\n");                     selection = Convert.ToInt32(Console.ReadLine());                     /*if statement which checks if the user wanted to end the                       program of if they entered a selection between 1 and 5*/                     if (selection == 5)                         Console.WriteLine("Exiting program.");                     else if (selection < 1 || selection > 5)                         Console.WriteLine("Please enter a selection between 1 and 5.\n");                     else                         SelectionMethod(selection);                 }//end try                 //if input value is not numeric, display message                 catch                 {                     Console.WriteLine("Invalid input value.");                 }//end catch             }//end while         }//end Main method         public static int SelectionMethod(int s)         {                 //declare variables and create reference to WeightConverter class             WeightConverter weightConverter = new WeightConverter();             decimal grams = 0;             decimal kilograms = 0;             decimal ounces = 0;             decimal pounds = 0;                                     try             {                                 switch (s)                 {                     //if user chose to input grams, prompt user to enter how many                     case 1:                         Console.WriteLine("Input amount of grams to be converted:\n");                         grams = Convert.ToDecimal(Console.ReadLine());                         //call Grams method of class WeightConverter                         weightConverter.Grams(grams);                         break;                     //if user chose to input kilograms, prompt user to enter how many                     case 2:                         Console.WriteLine("Input amount of kilograms to be conveted:\n");                         kilograms = Convert.ToDecimal(Console.ReadLine());                         //call Kilograms method of class WeightConverter                         weightConverter.Kilograms(kilograms);                         break;                     //if user chose to input ounces, prompt user to enter how many                     case 3:                         Console.WriteLine("Input amount of ounces to be converted:\n");                         ounces = Convert.ToDecimal(Console.ReadLine());                         //call Ounces method of class WeightConverter                         weightConverter.Ounces(ounces);                         break;                     //if user chose to input pounds, prompt user to enter how many                     case 4:                         Console.WriteLine("Input amount of pounds to be converted:\n");                         pounds = Convert.ToDecimal(Console.ReadLine());                         //call Pounds method of class WeightConverter                         weightConverter.Pounds(pounds);                         break;                 }             }//end try             //if input value is not numeric, display message             catch             {                 Console.WriteLine("Invalid input value.");             }//end catch             return s;         }//end Selection method     } } WeightConverter Class using System; using System.Collections.Generic; using System.Text; namespace Final_Question_3 {     class WeightConverter     {         public decimal Grams(decimal g)         {             //declare variables             decimal kilograms = 0;             decimal ounces = 0;             decimal pounds = 0;             int selection = 0;             while (selection <= 4)             {                 try                 {                     //prompt user to select what they would like to convert grams to                     Console.WriteLine("Convert grams to?\n1) Kilograms\t2) Ounces \t3) Pounds" +                             "\n4) Return to first selection.");                     selection = Convert.ToInt32(Console.ReadLine());                     switch (selection)                     {                         //convert grams to kilograms                         case 1:                             kilograms = g / 1000;                             Console.WriteLine("{0} gram(s) is {1} kilogram(s).", g, kilograms);                             break;                         //convert grams to ounces                         case 2:                             ounces = g / (int)28.31257;                             Console.WriteLine("{0} gram(s) is {1} ounce(s).", g, ounces);                             break;                         //convert grams to pounds                         case 3:                             pounds = g / 453;                             Console.WriteLine("{0} gram(s} is {1} pound(s).", g, pounds);                             break;                         //return to first selection                         case 4:                             selection = 5;                             break;                     }                 }//end try                 //if value entered is not numeric, display message                 catch                 {                     Console.WriteLine("Invalid input value.");                 }//end catch             }//end while             return g;         }         public decimal Kilograms(decimal kg)         {             decimal grams = 0;             decimal ounces = 0;             decimal pounds = 0;             return kg;         }         public decimal Ounces(decimal o)         {             decimal grams = 0;             decimal kilograms = 0;             decimal pounds = 0;             return o;         }         public decimal Pounds(decimal p)         {             decimal grams = 0;             decimal kilograms = 0;             decimal ounces = 0;             return p;         }     } }