Most efficient way to concatenate strings?

Question

What\'s the most efficient way to concatenate strings?

Answer 1

Rico Mariani, the .NET Performance guru, had an article on this very subject. It's not as simple as one might suspect. The basic advice is this:

If your pattern looks like:

x = f1(...) + f2(...) + f3(...) + f4(...)

that's one concat and it's zippy, StringBuilder probably won't help.

If your pattern looks like:

if (...) x += f1(...)
if (...) x += f2(...)
if (...) x += f3(...)
if (...) x += f4(...)

then you probably want StringBuilder.

Yet another article to support this claim comes from Eric Lippert where he describes the optimizations performed on one line + concatenations in a detailed manner.