sending otp in email after submit form

Question

i am done email sending after submit the form.but i can`t send otp to email.

[AllowAnonymous]
[Route("Register")]
public async Task<IHttpActionResult> Register(RegisterBindingModel model)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    var user = new ApplicationUser() { UserName = model.Email, Email = model.Email };

    IdentityResult result = await UserManager.CreateAsync(user, model.Password);

    if (!result.Succeeded)
    {
        return GetErrorResult(result);
    }
    MailMessage mm = new MailMessage("fromemail", "toemail");
    mm.Subject ="Leave Reject";
    mm.Body = "Hi Sir, " ;
    mm.IsBodyHtml = false;
    SmtpClient smtp = new SmtpClient();
    smtp.Host = "smtp.gmail.com";
    smtp.Port = 587;
    smtp.UseDefaultCredentials = false;
    smtp.Credentials = new System.Net.NetworkCredential("email", "password");
    smtp.EnableSsl = true;
    smtp.Send(mm);

    return Ok();
}