using System;

using OtpNet;

public class Program

{

    public static void Main()

    {

        //Reference - https://www.nuget.org/packages/Otp.NET 

        int otpValidityInSeconds = 5; //5 Seconds

        int otpSize = 6; //This is how many digits do you want your OTP code to be

        var otp = MultiFactorAuthenticationHelper.GetFactorCode("ashu",otpValidityInSeconds,otpSize);

        Console.WriteLine("Generated OTP is = "+ otp);

        Console.WriteLine(string.Format("\nIt is valid for {0} seconds and is of {1} digits",otpValidityInSeconds,otpSize));

    }   

    public static class MultiFactorAuthenticationHelper

    {    

    public static string GetFactorCode(string otpKeyStr, int otpValidityInSeconds,int otpSize)

    {

        var otpKeyBytes = Base32Encoding.ToBytes(otpKeyStr);

        var totp = new Totp(otpKeyBytes, step: otpValidityInSeconds, totpSize:otpSize);

        var twoFactorCode = totp.ComputeTotp();

        return twoFactorCode;

     } 

    }  

}