Topic 10018 min readStructured Tutorial

Introduction to Generics in C#

Quick Answer

Generics in C# allow you to define classes, methods, and data structures with a placeholder for the type of data they store or use. This enables type-safe, reusable code without sacrificing performance or requiring casts.

Learning Objectives

Explain the purpose of Introduction to Generics in a practical learning context.
Identify the main ideas, terms, and decisions involved in Introduction to Generics.
Apply Introduction to Generics in a simple real-world scenario or practice task.

Introduction

Generics are a powerful feature in C# that allow you to write flexible and reusable code. Instead of specifying exact data types, generics let you define placeholders that are replaced with actual types when the code is used.

This approach improves type safety and performance by eliminating the need for casting and boxing, common in non-generic collections and methods.

"Write once, use with any type."

What Are Generics?

Generics enable you to create classes, methods, interfaces, and delegates with a type parameter. This parameter is specified when you instantiate or call them, allowing the same code to work with different data types.

They help reduce code duplication and increase maintainability by providing a single implementation that works for multiple types.

Define type parameters using angle brackets, e.g., <T>.
Type parameters can be constrained to enforce certain behaviors.
Generics improve type safety by catching type errors at compile time.

Benefits of Using Generics

Generics offer several advantages over non-generic code, especially when working with collections or reusable components.

Type safety: Prevents runtime errors due to invalid casts.
Performance: Avoids boxing/unboxing with value types.
Code reuse: Write once, use with any compatible type.
Cleaner code: Reduces clutter from type checks and casts.

Generic Classes and Methods

You can define generic classes and methods by specifying type parameters. These parameters act as placeholders for actual types used when creating instances or invoking methods.

This flexibility allows you to create data structures and algorithms that work with any data type.

Example: Generic Class

Here is a simple generic class that stores a value of any type:

Example: Generic Method

You can also create generic methods inside non-generic or generic classes to operate on different types.

Type Constraints

Sometimes you want to restrict the types that can be used with generics. C# allows you to apply constraints to type parameters to enforce certain capabilities or inheritance.

where T : struct — T must be a value type.
where T : class — T must be a reference type.
where T : new() — T must have a parameterless constructor.
where T : BaseClass — T must inherit from BaseClass.
where T : interfaceName — T must implement the interface.

Practical Example

This generic class Box<T> can store an item of any type specified when creating an instance.

This generic method Swap<T> swaps two variables of any type passed by reference.

Examples

Generic Class Example

public class Box<T>
{
    private T content;

    public void Add(T item)
    {
        content = item;
    }

    public T Get()
    {
        return content;
    }
}

This generic class Box<T> can store an item of any type specified when creating an instance.

Generic Method Example

public class Utilities
{
    public static void Swap<T>(ref T a, ref T b)
    {
        T temp = a;
        a = b;
        b = temp;
    }
}

This generic method Swap<T> swaps two variables of any type passed by reference.

Best Practices

Use meaningful type parameter names, like TItem or TKey, for clarity.
Apply constraints only when necessary to keep generics flexible.
Avoid overusing generics if simpler types suffice.
Test generic code with multiple data types to ensure correctness.

Common Mistakes

Not applying constraints when required, leading to runtime errors.
Using overly generic type parameter names like T without context.
Casting generic types unnecessarily, defeating type safety.
Ignoring performance implications with complex generic hierarchies.

Hands-on Exercise

Create a Generic Stack Class

Implement a generic Stack<T> class with Push, Pop, and Peek methods.

Expected output: A functional generic stack that works with any data type.

Hint: Use an internal list or array to store elements and manage the stack behavior.

Implement a Generic Method to Find Maximum

Write a generic method that returns the maximum of two values of any comparable type.

Expected output: A method that correctly returns the larger of two values.

Hint: Use the 'where T : IComparable<T>' constraint and CompareTo method.

Interview Questions

What are generics in C# and why are they useful?

Interview

Generics allow you to define classes, methods, and interfaces with placeholders for data types, enabling type-safe and reusable code. They reduce code duplication and improve performance by avoiding boxing and casting.

How do you constrain a generic type to be a reference type?

Interview

You use the 'where T : class' constraint to restrict the generic type parameter T to reference types.

What is Introduction to Generics, and why is it useful?

Beginner

Generics in C# allow you to define classes, methods, and data structures with a placeholder for the type of data they store or use.

MCQ Quiz

1. What is the best first step when learning Introduction to Generics?

A. Understand the purpose and basic idea

B. Skip directly to advanced implementation

C. Ignore examples and practice

D. Memorize terms without context

Correct answer: A

Starting with the purpose and basic idea makes later examples and practice easier to understand.

2. Which activity helps reinforce Introduction to Generics?

A. Reading once without practice

B. Building or writing a small practical example

C. Avoiding review questions

D. Skipping the summary

Correct answer: B

A small practical example helps connect the topic to real usage.

3. Which statement is most accurate about this topic?

A. Generics in C# allow you to define classes, methods, and data structures with a placeholder for the type of data they store or use.

B. Introduction to Generics never needs examples

C. Introduction to Generics is unrelated to practical work

D. Introduction to Generics should be learned without checking results

Correct answer: A

The correct option is based on the available topic explanation.

Key Takeaways

Generics in C# allow you to define classes, methods, and data structures with a placeholder for the type of data they store or use.
This enables type-safe, reusable code without sacrificing performance or requiring casts.
Generics are a powerful feature in C# that allow you to write flexible and reusable code.
Instead of specifying exact data types, generics let you define placeholders that are replaced with actual types when the code is used.
This approach improves type safety and performance by eliminating the need for casting and boxing, common in non-generic collections and methods.

Summary

Generics are a fundamental feature in C# that enable you to write reusable, type-safe code components.

By using type parameters and constraints, you can create flexible classes and methods that work with various data types without sacrificing performance or safety.

Understanding and applying generics effectively improves code quality and maintainability.

Frequently Asked Questions

Can generics be used with value types and reference types?

Yes, generics in C# work with both value types (like int, struct) and reference types (like classes).

What happens if you don't apply constraints to a generic type?

Without constraints, the generic type can be any type, but you cannot assume any specific members or behaviors, which may limit what operations you can perform.

Are generics in C# similar to templates in C++?

Yes, both provide a way to write type-agnostic code, but C# generics are implemented differently with runtime type safety and constraints.

What is Introduction to Generics?