Sealed Class in C# – Explained with Real-Life Example
When working with object-oriented programming in C#, you might come across the term sealed class. But what exactly is a sealed class, and when should you use one? In this article, we’ll dive into the concept of sealed classes, explore their pros and cons, and walk through a practical example that you can relate to real-world scenarios.
What is a Sealed Class?
A sealed class is a class that cannot be inherited. In C#, you define a sealed class using the sealed keyword before the class name. This is helpful when you want to restrict other classes from extending your class, thus preserving the behavior and design.
public sealed class PaymentProcessor
{
public void ProcessPayment()
{
Console.WriteLine("Processing payment...");
}
}In this example, PaymentProcessor is a sealed class. No other class can inherit from it.
Advantages of Sealed Classes
1.Better Performance
Since the compiler knows that the class won’t be extended, it can optimize method calls at compile time, especially in scenarios involving virtual methods.
2.Security and Control
Sealed classes prevent other developers from unintentionally or maliciously altering your class behavior by inheritance.
3.Simplifies Maintenance
Because there’s no subclassing, the code is easier to reason about and maintain over time.
4.Encapsulation Enforcement
It enforces encapsulation by not allowing the extension of internal logic, which is crucial in sensitive domains like banking or payment gateways.
Disadvantages of Sealed Classes
- No Extensibility
Once a class is sealed, it can’t be extended. This limits flexibility, especially if you later decide to reuse some functionality via inheritance. - Testing Challenges
Sealed classes can be harder to mock or stub in unit tests, particularly if they don’t implement interfaces. - Design Limitations
Sealing a class too early might restrict future developers from adapting it to new requirements.
Real-World Example: Sealed Class in a Payment System
Let’s say you’re building an e-commerce platform and you have a class called PaymentProcessor that connects to a third-party payment gateway. You don’t want anyone to override its methods or alter its functionality due to compliance and security concerns. Here’s how you’d use a sealed class:
public sealed class PaymentProcessor
{
public void ProcessCreditCard(string cardNumber, decimal amount)
{
// Logic to securely process payment
Console.WriteLine($"Charged {amount} to credit card ending with {cardNumber[^4..]}.");
}
}By sealing this class, you ensure that the core payment logic remains untouched, secure, and consistent across your application.
Now, if someone tries to inherit from it:
public class CustomPaymentProcessor : PaymentProcessor // ❌ Compile-time error
{
// This will not work
}This prevents any accidental overrides that could break payment flows or introduce vulnerabilities.
A sealed class in C# is a great tool when you want to lock down a class’s behavior. It improves performance, enhances security, and simplifies maintenance. However, it’s essential to use it wisely. Sealing a class too early in development may limit flexibility and make testing harder.
If you’re designing core components like utility classes, payment gateways, or logging systems—sealed classes are worth considering.
