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Generics

By SHANTILAL

Reusability in C#:

C# lets you reuse code in two major ways:

  1. Inheritance
  2. Generics
Let’s look at each:

1. Inheritance:

  • Inheritance is an object-oriented concept.
  • You write a base class and then extend it to create more specific classes.
  • Example:
     class Animal 
     {
           public void Eat() { Console.WriteLine("Eating..."); }
     }

     class Dog : Animal 
     {
           public void Bark() { Console.WriteLine("Barking..."); }
     }

     // Reusing code via inheritance
    Dog d = new Dog();
    d.Eat(); // From Animal
    d.Bark(); // From Dog

✅ Pros: Useful when classes share common behavior.
❌ Cons: Less flexible when working with types (like int, string, etc.)

2. Generics:

  • Generics allow you to write code using placeholder types.
  • Instead of writing multiple versions of the same class or method for different types (e.g., int, string), you write one generic version.
  • Example:
     class Box<T> 
     {
        public T Value;
     }

    Box<int> intBox = new Box<int> { Value = 123 };
    Box<string> strBox = new Box<string> { Value = "Hello" };

Here, T is a placeholder type — it could be anything.

✅ Why Generics are Better in Some Cases?

1. Type Safety:
  • Generics know the type at compile-time.
  • You get intellisense and compile-time errors if you use the wrong type.
     Box<int> b = new Box<int>();
     b.Value = "Hello"; // ❌ Compile-time error

2. No Boxing/Unboxing:
  • Boxing happens when a value type (like int) is converted to an object (reference type).
  • Generics avoid this, so they’re more efficient.
     object x = 5; // boxing
     int y = (int)x; // unboxing
  • If you use List<object>, you’d box every value type.
  • With List<int>, there’s no boxing.

📦 Real-Life Example: Storage Box


🧠 Imagine:

You are building a program to manage storage boxes.

Each box can store only one item, but it could be an item of any type — a book, a toy, a shirt, etc.

❌ Without Generics:

You might create different classes for each type:

class BookBox 
{
  public Book Item;
}

class ToyBox 
{
    public Toy Item;
}

That's a lot of repetitive code and not scalable!

✅ With Generics:

Use one generic class for all types of boxes:

class StorageBox<T> 
{
    public T Item { get; set; }
}

Now you can create boxes for any type:

StorageBox<string> bookBox = new StorageBox<string>();
bookBox.Item = "C# Programming Book";

StorageBox<int> numberBox = new StorageBox<int>();
numberBox.Item = 123;

StorageBox<DateTime> dateBox = new StorageBox<DateTime>();
dateBox.Item = DateTime.Now;

🔐 Benefits:

  • ✔ Type-safe: You can't accidentally put a DateTime in a StorageBox<string>.

  • ✔ Reusable: One class handles all types.

  • ✔ Clean code: No code duplication.

🧾 Real Code Example:

using System;

class StorageBox<T>
{
    public T Item { get; set; }
}

class Program
{
    static void Main()
    {
        var fruitBox = new StorageBox<string> { Item = "Apple" };
        var numberBox = new StorageBox<int> { Item = 42 };

        Console.WriteLine($"Fruit: {fruitBox.Item}");
        Console.WriteLine($"Number: {numberBox.Item}");
    }
}

Output:

Fruit: Apple
Number: 42


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