only problem with this program is that when I enter 'z' to exit it works but when I try'Z' it does not work. pls help using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace assignment2_nepal {     class sales     {         public char empname;         Double indsale;         Double indsaleA = 0;         Double indsaleB = 0;         Double indsaleE = 0;         Double indcomsaleA = 0;         Double indcomsaleB = 0;         Double indcomsaleE = 0;         const Double commrate = 0.10;         public void TotalSales()         {             Console.WriteLine("Enter A for Andrea or B or Brittany or E for Eric or z to quit:");             Console.WriteLine("Enter a salesperson initial:");             empname = Convert.ToChar(Console.ReadLine());             while (empname !== 'z' || empname=='Z')             {                                    if (empname == 'A' || empname == 'a')                     {                         Console.Out.WriteLine("Enter amount of sale");                         indsale = Convert.ToDouble(Console.ReadLine());                         indsaleA = indsaleA + indsale;                     }                     else if (empname == 'B' || empname == 'b')                     {                         Console.Out.WriteLine("Enter amount of sale");                         indsale = Convert.ToDouble(Console.ReadLine());                         indsaleB = indsaleB + indsale;                     }                     else if (empname == 'E' || empname == 'e')                     {                         Console.Out.WriteLine("Enter amount of sale");                         indsale = Convert.ToDouble(Console.ReadLine());                         indsaleE = indsaleE + indsale;                     }                     else                         Console.Out.WriteLine("Invalid Entry! Please enter A, B or E for sales Employee and z to Quit");                     Console.WriteLine("Enter another salesperson or z to quit");                     empname = Convert.ToChar(Console.ReadLine());                 }             }                public void computesales()         {             indcomsaleA = commrate * indsaleA;             indcomsaleB = commrate * indsaleB;             indcomsaleE = commrate * indsaleE;         }         public void PrintSales()         {             Console.WriteLine("Andrea earned:               ${0}", indcomsaleA);             Console.WriteLine("Brittany earned:             ${0}", indcomsaleB);             Console.WriteLine("Eric earned:                 ${0}", indcomsaleE);         }     }     class assignment2_nepal     {         static void Main(String[] args)         {             sales sale = new sales();             sale.TotalSales();             sale.computesales();             sale.PrintSales();         }     } }