What's the most efficient way to change the last element in a '/' delimited string

Question

I have a string object in c# with a bunch of elements delimited by '/' characters. The string will look something like this:

"element1/element2/element3/element4"

What's the most efficient way to change the last element in the '/' delimited string?

Answer 1

Use string.LastIndexOf:

string s = "element1/element2/element3/element4";
s = s.Substring(0, s.LastIndexOf('/') + 1) + "foo";