string.format efficiency with conditional spacing

Question

What's the absolute fastest way to format a full name? where the middlename and suffix might be null or empty?

string fullname = string.Format("{0} {1} {2} {3}", 
                                FName, 
                                MI, 
                                LName, 
                                Suffix);

The problem with this is that if the MI or suffix is empty, then I have two spaces.

I could make a second pass with this:

fullname = fullname.Replace("  ", " ");

or I could just make the string with something like this:

string fullname = string.Format("{0}{1} {2}{3}", 
                        FName, 
                        string.IsNullOrEmpty(MI) ? "" : " " + MI, 
                        LName, 
                        string.IsNullOrEmpty(Suffix) ? "" : " " + Suffix);

Is there a better option? Fastest is the important thing.

Answer 1

Check first for null-or-empty and then write specialized code for each of them. I'd expect directly working on a char[] buffer to be faster than string.Format or StringBuilder.

But I find it strange that formatting names is a performance bottleneck in your application. Even formatting a few million names shouldn't take that long.

Answer 2

I would do this:

var parts = new[] { FName, MI, LName, Suffix };
string fullName = string.Join(" ", parts.Where(s => !string.IsNullOrWhiteSpace(s)));

It's probably not the fastest solution, but it makes it pretty clear what's going on.