String.Join performance issue in C#

Question

I\'ve been researching a question that was presented to me: How to write a function that takes a string as input and returns a string with spaces between the characters. Th

Answer 1

When you have passed an IEnumerable to String.Join, it has no idea on how much memory needs to be allocated. I allocates a chunk of memory, resizes it if it is insufficient and repeats the process until it gets enough memory to accommodate all the strings.

The array version is faster because we know the amount of memory allocated well ahead.

Also please not that when you are running the 1st version, GC might have occurred.