Have you ever written the same logic multiple times because you needed to support different data types?

C# Generics help solve this problem by allowing developers to create classes, interfaces, methods, and delegates that work with different types while maintaining compile-time type safety.

1. What are Generics?

Generics let you define a type or method using a type parameter, commonly represented by T.

For example:

public T GetValue<T>(T value)
{
    return value;
}

You can call this method with different types:

int number = GetValue(10);
string name = GetValue("Faiz");

The same method works with both values without requiring separate implementations.

2. Why are Generics useful?

Type safety: The compiler checks that you use compatible types, reducing the need for unsafe casts.

Code reusability: Instead of duplicating logic for integers, strings, and other types, you can reuse a generic implementation.

Performance: Generic collections avoid the boxing and unboxing overhead associated with storing value types in non-generic collections such as ArrayList.

Maintainability: One well-designed generic class can replace several nearly identical classes.

3. Where will you find Generics in .NET?

You probably already use generics in your daily work:

• List<T> — stores a collection of a specific type.
• Dictionary<TKey, TValue> — stores key-value pairs.
• Task<T> — represents an asynchronous operation that produces a result.
• IEnumerable<T> — provides a strongly typed way to enumerate values.

For example:

List<int> numbers = [1, 2, 3];
List<string> names = ["Faiz", "Ahmed"];

Both collections use the same generic collection type but enforce different element types.

4. What are Generic Constraints?

Sometimes, a generic method needs to restrict which types it accepts.

public class Repository<T> where T : class
{
    // T must be a reference type.
}

The where T : class constraint tells the compiler that T must be a reference type. Other constraints can require an interface, a base class, or a parameterless constructor.

Final Thoughts

Generics are essential for building reusable libraries, maintainable services, and type-safe .NET applications.

Don’t just learn the syntax. Look at the generic types you already use in ASP.NET Core and understand how they help reduce duplication and improve type safety.

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