Question

For example:

List<MyClass> myList = new List<MyClass>();
...
// add lots of members...
...
MyClass myClass = myList[25];

Will asking for index 25 take much longer than asking for index 1, or does it use some quick algorithm to jump straight to the 25th item?

Thanks!

Answer 1

Internally List<T> is implemented as array (which grows when you’re adding new items) so accessing of n-th element will be O(1) operation. (Therefore there will be no difference in speed between getting myList[1] and myList[25].)

Excerpt from the List<T>.Item property documentation:

Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.

I can imagine how slow would be .NET applications if List<T> had to jump through all items before getting n-th…