Question

Whats is correct to do?

check if exists, then remove?

var input = "foo #main baa"; 
if(input.Contains("#main")) {
   input = input.Replace("#main", "");
}

or just:

input = input.Replace("#main", "");

Well, this seem a simple question,but I really want know.
Thanks in advance.

Answer 1

The Contains check actually just makes your code slower.
Remove it.

The Contains call needs to loop through the string until it finds #main.
The Replace call then needs to do the same exact loop (it can’t remember it from the Contains call).
This is a Shlemiel the Painter’s algorithm.

Replace can handle strings with zero or more occurrences of the search string, so you don’t need the check.