using System;                   

public class Program

{

    public static void Main()

    {       

        string UserName = "";

        string Password = "";       

        string[] ValidUserNames = new string[]{"admin","Joe","Jane"};

        string[] ValidPasswords = new string[]{"pass","1234","!@#$"};

        bool ValidCredentialsFlag = false;

        do

        {

            Console.WriteLine("User Name: "); UserName = Console.ReadLine();        

            Console.WriteLine("Password: "); Password = Console.ReadLine();             

            int userToCheck = 0;

            do

            {

                ValidCredentialsFlag = CredentialValidationCheck(UserName, Password, ValidUserNames[userToCheck],ValidPasswords[userToCheck]);

                userToCheck++; 

            }while(userToCheck < ValidUserNames.Length && ValidCredentialsFlag == false);           

​

            if(ValidCredentialsFlag == false) Console.WriteLine("Invalid Login Credentials");

        }while(ValidCredentialsFlag == false);

        Console.WriteLine("Successful Login");

    }//Main

    public static bool CredentialValidationCheck(string userNameToCheck, string passWordToCheck, string validUserName, string validPassword)

    {       

        if(userNameToCheck == validUserName && passWordToCheck == validPassword)

            return true;

        else

            return false;

    }

}