Guard Classes: Bulletproof your C# Applications

Yes, not many people actually know about those.

Alex Maher

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Understanding Guard Classes in C#

Ever had that “Uh-oh” moment in programming when you realize your method is processing something it shouldn’t?

That’s where guard classes in C# come to the rescue.

They’re like the little checks we do in our daily lives, like glancing at our coffee cup to make sure it’s not too full before we start walking.

Ok let’s dive in!

The Role of Guard Classes

  1. Error Prevention: Guard classes act as a first line of defense, ensuring that only valid data passes through. They’re like the filters that catch the debris before it clogs up the system.
  2. Cleaner Code: By outsourcing validation logic to guard classes, your main code stays clean and focused on its primary purpose.
  3. Reusability: Once you’ve crafted a guard class, it can be reused across different parts of your application, promoting consistency and saving time.

Implementing a Basic Guard Class

Let’s look at a simple example. Imagine you have a method that processes user data. The catch is, you need to ensure that the user’s age is above a certain threshold.

public class Guard
{
public static void AgainstInvalidAge(int age, int minAge)
{
if (age < minAge)
{
throw new ArgumentException($"Age must be greater than {minAge}");
}
}
}

In your method, you’d use this guard class like so:

public void ProcessUserData(int age)
{
Guard.AgainstInvalidAge(age, 18); // Ensures age is 18 or above
// Rest of the method logic
}

Advanced Usage: Generic Guard Methods

For more complex scenarios, you might want to create generic guard methods that can handle different data types and validation scenarios. This approach further increases the versatility of your guard classes.

public static class Guard
{
public static void AgainstNull<T>(T input, string paramName)
{…

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Alex Maher

.NET C# dev with 10+ yrs exp, self-taught & passionate web developer. Sharing tips & experiences in C# and web dev.