C# List vs Array: Performance & Usage Guide

C# List is a dynamic collection that grows and shrinks at runtime; C# Array is a fixed-size, indexed sequence created at compile-time.

Developers often pick one, then hit runtime crashes or memory bloat. The confusion: both store elements, both use brackets, but only one lets you `Add()` mid-loop without reallocating the universe.

Key Differences

Array: fixed length, faster indexed reads, value-type storage, declared `int[] nums = new int[5];`. List: resizable, slightly slower, stores references, declared `var nums = new List();`, reallocates internally when capacity is exceeded.

Which One Should You Choose?

Need speed and size never changes? Array. Need insert/remove, LINQ, or unknown length? List. In performance-critical loops, cache-friendly arrays win; everywhere else, List keeps code sane.

Examples and Daily Life

Pixel buffer in a game engine: `Color[] frame = new Color[1920*1080];`. Storing chat messages: `List inbox = new();`. Arrays for raw data, Lists for user data—pick the mental model that matches the domain.

Can I convert a List to an Array?

Yes—call `ToArray()`; it copies references into a new fixed block.

Is List slower than Array?

Slightly; each `Add` may reallocate, and indexing has bounds checks, but the JIT often inlines the overhead away.

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