1. Install Nuget Package.

Install Nuget Package https://www.nuget.org/packages/OnlyOTP

2. Generate OTP

var otpProvider = new Otp();
//Generates 6 digit OTP by default
var otp = otpProvider.GenerateOtp();

Advanced Options

Generate OTP with specified length

var otpWithSpecifiedLength = otpProvider.GenerateOtp(new OtpOptions { Length = 10 });

Gerenate OTP and Store In-Memory

Install InMemory OTP Storage Nuget

Install additional Nuget Package https://www.nuget.org/packages/OnlyOtp.Storage.InMemory

Instantiate Otp with InMemoryOtpStorage

public void SomeMethod()
{
    // Pass InMemoryOtpStorage to Otp Provider.
    var otpProvider = new Otp(new InMemoryOtpStorage());

    // Returns OTP and OTP Verification Token
    // Save this token to retreive generated OTP later

    (string myOtp, string myToken) = otpProvider.GenerateAndStoreOtp();
}
public void SomeOtherMethod(string otpEnteredByUser)
{
    // Match the stored OTP with OTP entered by user
    var isMatched = otpProvider.IsOtpMached(otpEnteredByUser, myToken);
}

Generate OTP and Store in SQL Server

Install InMemory OTP Storage Nuget

Install additional Nuget Package https://www.nuget.org/packages/OnlyOtp.Storage.SqlServer

Create table and schema

SqlServerOtpStorage uses an Sql Server to store OTPs. Use this script to generate necessary table and schema.

GO
CREATE SCHEMA [OnlyOtp]
GO
CREATE TABLE [OnlyOtp].[Otp](
	[Id] [nvarchar](100) NOT NULL,
	[Value] [nvarchar](100) NOT NULL,
 CONSTRAINT [PK_Otp] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)) ON [PRIMARY]
GO

Create DbContext

In an ASP.NET Core application

If you’re using ASP.NET Core, you can use Dependency Injection to set-up DbContext used by OnlyOtp.

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.AddDbContext<OnlyOtpContext>(options =>
    {        
        options.UseSqlServer(@"Data Source=DATABASE_SERVER_NAME;Initial Catalog=DATABASE_NAME;Integrated Security=True;");
    });
    ...
}

And in Controller or any other class, inject this DbContext:

public class HelloController : Controller
{
    private readonly OnlyOtpContext _onlyOtpContext;

    public HelloController(OnlyOtpContext onlyOtpContext)
    {
        _onlyOtpContext = onlyOtpContext;
    }
    
}

In any other application

You can instantiate the DbContext manually.

var options = new DbContextOptionsBuilder<OnlyOtpContext>()
                .UseSqlServer(@"Data Source=DATABASE_SERVER_NAME;Initial Catalog=DATABASE_NAME;Integrated Security=True;")
                .Options;
var dbContext = new OnlyOtpContext(options);

Use Otp with SqlServerOtpStorage

public void SomeMethod()
{
    // Pass SqlServerOtpStorage to Otp Provider.
    var otpProvider = new Otp(new SqlServerOtpStorage(_onlyOtpContext));
    // Get OTP token and generated OTP
    (string otp, string token) = otpProvider.GenerateAndStoreOtp();
    //Save this token to retreive generated OTP later
    ...
}
public void SomeOtherActionMethod(string otpEnteredByUser)
{
    ...
    // Match the stored OTP with OTP entered by user
    bool isOtpMatched = otpProvider.IsOtpMached(otpEnteredByUser, token);
    ...
}