Method for generating and mailing "magic links"

SendSignInLinkAsync.cs

 protected async Task SendSignInLinkAsync()
{            
    string email = mailer.to.Email;
    string token = BuildIdToken(email);
    string link = BuildUrl(token);            
    string htmlTemplate = System.IO.File.ReadAllText("SignInTemplate.html");

    var apiKey = configuration.GetSection("MailerSettings")["SendGridApiKey"];            
    var client = new SendGridClient(apiKey);
    var plainTextContent = "You should be seeing a SignIn link below.";
    var htmlContent = string.Format(htmlTemplate, email, link);
    var msg = MailHelper.CreateSingleEmail(mailer.from, mailer.to, mailer.subject, plainTextContent, htmlContent);
    var response = await client.SendEmailAsync(msg);
}
private string BuildIdToken(string Email)
{
    string B2CClientId = configuration.GetSection("MailerSettings")["B2CClientId"];
    double LinkExpiresAfterMinutes;
    double.TryParse(configuration.GetSection("MailerSettings")["LinkExpiresAfterMinutes"], out LinkExpiresAfterMinutes);

    string issuer = configuration.GetSection("MailerSettings")["issuer"];

    // All parameters sent to Azure AD B2C needs to be sent as claims
    IList<System.Security.Claims.Claim> claims = new List<System.Security.Claims.Claim>
    {
        new System.Security.Claims.Claim("email", Email, System.Security.Claims.ClaimValueTypes.String, issuer)
    };

    // Create the token
    JwtSecurityToken token = new JwtSecurityToken(
            issuer,
            B2CClientId,
            claims,
            DateTime.Now,
            DateTime.Now.AddMinutes(LinkExpiresAfterMinutes),
            SigningCredentials.Value);

    // Get the representation of the signed token
    JwtSecurityTokenHandler jwtHandler = new JwtSecurityTokenHandler();

    return jwtHandler.WriteToken(token);
}

private string BuildUrl(string token)
{
    string B2CSignInUrl = configuration.GetSection("MailerSettings")["B2CSignInUrl"];

    return $"{B2CSignInUrl}?id_token_hint={token}";
}