C#•2mo ago

List, Collection Initializer and Capacity

Hi! Does creating a new List with new List<T> { new T() } (or any number of elements > 0) starts with the proper capacity in order to avoid resizes or does it start at 0 and then grows to add the elements and I should be using new List<T>(1) { new T() } (for instance) instead? Thanks for helping me figure this out!

43 Replies

Unknown User•2mo ago

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ikalou.•2mo ago

I think the docs say new List<T> starts at 0 (instead of 4)?

MODiX•2mo ago

TeBeCo

REPL Result: Success

(new List<int>()).Capacity

(new List<int>()).Capacity

Result: int

Compile: 204.168ms | Execution: 17.922ms | React with ❌ to remove this embed.

Unknown User•2mo ago

Message Not Public

MODiX•2mo ago

TeBeCo

REPL Result: Success

(new List<int>() {1}).Capacity

(new List<int>() {1}).Capacity

Result: int

Compile: 268.383ms | Execution: 25.126ms | React with ❌ to remove this embed.

Unknown User•2mo ago

Message Not Public

MODiX•2mo ago

TeBeCo

REPL Result: Success

(new List<int>(3) {1}).Capacity

(new List<int>(3) {1}).Capacity

Result: int

Compile: 234.006ms | Execution: 27.054ms | React with ❌ to remove this embed.

Unknown User•2mo ago

Message Not Public

SleepWellPupper•2mo ago

var l = new List<T>()
{
  new T(),
  new T(),
  new T()
}

var l = new List<T>()
{
  new T(),
  new T(),
  new T()
}

gets turned into

var l = new List<T>();
l.Add(new T());
l.Add(new T());
l.Add(new T());

var l = new List<T>();
l.Add(new T());
l.Add(new T());
l.Add(new T());

To answer your question

MODiX•2mo ago

TeBeCo

REPL Result: Success

var l = new List<int>();
l.Add(1);
l.Capacity

var l = new List<int>();
l.Add(1);
l.Capacity

Result: int

Compile: 338.572ms | Execution: 21.330ms | React with ❌ to remove this embed.

SleepWellPupper•2mo ago

So it will grow accordingly

Unknown User•2mo ago

Message Not Public

ikalou.•2mo ago

My question is‚ when using a collection initializer with n elements‚ is new List<T>() {...} be as efficient as new List<T>(n) {...}. It would seem logical but I can't find the information nor do I know how to test it.

Unknown User•2mo ago

Message Not Public

MODiX•2mo ago

TeBeCo

REPL Result: Success

(new List<int>() {1}).Capacity

(new List<int>() {1}).Capacity

Result: int

Quoted by

<@689473681302224947> from #List, Collection Initializer and Capacity (click here)

Compile: 268.383ms | Execution: 25.126ms | React with ❌ to remove this embed.

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List, Collection Initializer and Capacity