
In today's digital world, an effective notification system is crucial for businesses and applications that need to engage users, provide updates, and maintain real-time communication.
Whether it's transactional messages, promotional emails, or urgent security alerts, a robust notification system ensures timely delivery across different channels—Email, SMS, and Push Notifications.
Building such a system from scratch presents several challenges, such as handling multiple channels, ensuring reliability, managing failures, and integrating with third-party providers.
This post explores:
- What makes a notification system robust
- How to integrate external services for Email (Gmail/SendGrid), SMS (EZ Texting), and Push (Firebase)
- A high-level design in .NET 9 using Clean Architecture and SOLID principles
By the end, you'll understand how to build a scalable and maintainable notification system in C# and .NET 9.
What Makes a Robust Notification System?
A modern notification system must be scalable, reliable, and multi-channel. Here are the key elements:
1. Multi-Channel Support
- Email (Gmail, SendGrid, AWS SES)
- SMS (EZ Texting, Twilio, Nexmo)
- Push Notifications (Firebase, OneSignal)
2. Reliability & Failure Handling
- Implement retry mechanisms for failed messages.
- Use message queues (e.g., RabbitMQ, Azure Service Bus) for async processing.
3. Prioritization & User Preferences
- Users should choose preferred channels (Email, SMS, or Push).
- Critical notifications (e.g., password reset) should be delivered immediately.
4. Logging & Monitoring
- Track sent notifications for debugging and compliance.
- Implement audit trails for troubleshooting failed messages.
5. Scalability
- Handle thousands of notifications without performance degradation.
- Use distributed architectures (e.g., microservices) for large-scale applications.
Integrating with External Providers
Instead of building an entire notification infrastructure, we can leverage industry-standard providers:
1. Email Notifications (Gmail/SendGrid)
- Emails are commonly used for account verifications, newsletters, and transactional alerts.
- We'll use Gmail SMTP for sending emails in .NET 9.
2. SMS Notifications (EZ Texting)
- SMS provides instant communication, useful for alerts and authentication.
- We'll integrate EZ Texting API to send SMS messages.
3. Push Notifications (Firebase)
- Push notifications are cost-effective for mobile and web applications.
- We'll use Firebase Cloud Messaging (FCM) to send push notifications.
High-Level Design of the Notification System
Architecture Overview
We'll follow Clean Architecture to structure the notification system. Here's a simplified layered architecture:
+----------------------+
| Presentation | --> Controllers or Background Services
+----------------------+
| Application | --> Use Cases (Send Notification)
+----------------------+
| Domain | --> Entities (Notification, NotificationType)
+----------------------+
| Infrastructure | --> External Integrations (Gmail, SMS, Firebase)
+----------------------+
Core Components
- Domain Layer —
Notification
entity & NotificationType
- Application Layer —
SendNotificationUseCase
- Infrastructure Layer — Email, SMS, and Push integrations
- Presentation Layer — API controllers or background workers
Implementing a Notification System in .NET 9
Now, let's look at the code implementation in C# and .NET 9.
1. Define the Notification Entity (Domain Layer)
public enum NotificationType
{
Email,
SMS,
Push
}
public class Notification
{
public Guid Id { get; set; }
public string Recipient { get; set; }
public string Message { get; set; }
public NotificationType Type { get; set; }
public DateTime SentAt { get; set; }
}
2. Implementing Use Case (Application Layer)
public class SendNotificationUseCase
{
private readonly IEmailService _emailService;
private readonly ISmsService _smsService;
private readonly IPushNotificationService _pushNotificationService;
public SendNotificationUseCase(
IEmailService emailService,
ISmsService smsService,
IPushNotificationService pushNotificationService)
{
_emailService = emailService;
_smsService = smsService;
_pushNotificationService = pushNotificationService;
}
public async Task SendNotificationAsync(Notification notification)
{
switch (notification.Type)
{
case NotificationType.Email:
await _emailService.SendEmailAsync(notification.Recipient, notification.Message);
break;
case NotificationType.SMS:
await _smsService.SendSmsAsync(notification.Recipient, notification.Message);
break;
case NotificationType.Push:
await _pushNotificationService.SendPushNotificationAsync(notification.Recipient, notification.Message);
break;
}
}
}
3. Implementing External Provider Integrations (Infrastructure Layer)
Email (Gmail SMTP Integration)
public class GmailEmailService : IEmailService
{
private readonly SmtpClient _smtpClient;
public GmailEmailService()
{
_smtpClient = new SmtpClient("smtp.gmail.com")
{
Port = 587,
Credentials = new NetworkCredential("your-email@gmail.com", "your-password"),
EnableSsl = true
};
}
public async Task SendEmailAsync(string recipient, string message)
{
var mailMessage = new MailMessage("your-email@gmail.com", recipient)
{
Subject = "Notification",
Body = message
};
await _smtpClient.SendMailAsync(mailMessage);
}
}
SMS (EZ Texting API Integration)
public class EzTextingSmsService : ISmsService
{
private readonly HttpClient _httpClient;
public EzTextingSmsService(HttpClient httpClient)
{
_httpClient = httpClient;
}
public async Task SendSmsAsync(string recipient, string message)
{
var payload = new { phoneNumber = recipient, message = message };
await _httpClient.PostAsJsonAsync("https://app.eztexting.com/api/send", payload);
}
}
Push Notifications (Firebase Cloud Messaging - FCM)
public class FirebasePushService : IPushNotificationService
{
private readonly FirebaseMessaging _firebaseMessaging;
public FirebasePushService(FirebaseMessaging firebaseMessaging)
{
_firebaseMessaging = firebaseMessaging;
}
public async Task SendPushNotificationAsync(string recipient, string message)
{
var notification = new Message
{
Token = recipient,
Notification = new Notification
{
Title = "New Notification",
Body = message
}
};
await _firebaseMessaging.SendAsync(notification);
}
}
Conclusion
A robust notification system is essential for user engagement, real-time alerts, and seamless communication. By using .NET 9 with Clean Architecture, you can:
- Scale notifications across multiple channels (Email, SMS, Push)
- Integrate with industry-leading providers (Gmail, EZ Texting, Firebase)
- Ensure reliability, scalability, and extensibility
Need a Custom Notification System? Our team specializes in .NET 9, Clean Architecture, and scalable messaging solutions. Contact i2b Global today to discuss your project!