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

Anubhav Sharma 393 19 Jun 2025

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

c# c#
Updated 23 Jun 2025
Anubhav Sharma
Anubhav Sharma

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The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

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1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 23 Jun 2025
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Generics in C# allow you to define classes, interfaces, methods, or delegates with a placeholder for the data type. This means you can write code that works with any data type while maintaining type safety and avoiding runtime casting.

Why Generics Are Useful:

Benefit Explanation
Type Safety Errors are caught at compile time instead of runtime.
Code Reusability You can write logic once and reuse it with different types.
Performance Avoids boxing/unboxing with value types.
Clarity Clear intent — you know what type is being used in advance.

Example: Without Generics

public class Box
{
    public object Item { get; set; }
}

var intBox = new Box();
intBox.Item = 123;

int value = (int)intBox.Item; // Requires casting

Problems:

  • No compile-time type check.
  • Requires casting → possible runtime exceptions.

With Generics:

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

var intBox = new Box<int>();
intBox.Item = 123;

int value = intBox.Item; // No casting, type-safe

Generic Method Example:

public T GetFirst<T>(List<T> items)
{
    return items.First();
}

Can be called as:

int first = GetFirst(new List<int> { 1, 2, 3 });
string firstStr = GetFirst(new List<string> { "a", "b" });

.NET Built-in Examples:

  • List<T>
  • Dictionary<TKey, TValue>
  • Task<T>
  • Nullable<T> (i.e., int?)

Summary:

Generics allow you to write:

  • Flexible, yet strongly typed code
  • Without duplicating logic for different types
  • And with better performance and safety

Let me know if you want to see:

  • Generic constraints (where T : class, etc.)
  • Generic interfaces
  • Comparisons with templates in C++
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