All 16 Collections questions
More in Collections
When should you use a Dictionary<TKey,TValue>? What is the difference between List<T> and an array (T[]) in terms of resizing? What is the difference between Dictionary<TKey, TValue> and List<T> in terms of lookup performance? What is the difference between IEnumerable, ICollection and IList? What does HashSet<T> provide and when do you use it? When would you choose a HashSet<T> over a List<T>, and what guarantee does it provide? How does Queue<T> differ from Stack<T> in terms of the order items are removed? What is the difference between IEnumerable<T>, ICollection<T>, and IList<T> in the collection interface hierarchy? When would you reach for a ConcurrentDictionary or an immutable collection? How do you avoid multiple enumeration of an IEnumerable?
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C# › Collections

When would you use a List<T> vs an array?

Beginner

Answer

Use an array for a fixed-size, performance-critical buffer; use List<T> when the count changes, since it grows and offers Add/Remove/Insert.
int[] fixedGrid = new int[9];
var items = new List<string>(); items.Add("a");
Real-world example A game board is an array; a shopping cart is a List<T>.
All 16 Collections questions