c# - String Concat using constants - performance

Question

Assume I have the following string constants:

const string constString1 = "Const String 1";
const string constString2 = "Const String 2";
const string constString3 = "Const String 3";
const string constString4 = "Const String 4";

Now I can append the strings in two ways: Option1:

string resultString = constString1 + constString2 + constString3 + constString4;

Option2:

string resultString = string.Format("{0}{1}{2}{3}",constString1,constString2,constString3,constString4);

Internally string.Format uses StringBuilder.AppendFormat. Now given the fact that I am appending constant strings, which of the options (option1 or option 2) is better with respect to performance and/or memory?

Answer 1

The first one will be done by the compiler (at least the Microsoft C# Compiler) (in the same way that the compiler does 1+2), the second one must be done at runtime. So clearly the first one is faster.

As an added benefit, in the first one the string is internalized, in the second one it isn't.

And String.Format is quite slow :-) (read this http://msmvps.com/blogs/jon_skeet/archive/2008/10/06/formatting-strings.aspx). NOT "slow enough to be a problem", UNLESS all your program do all the day is format strings (MILLIONS of them, not TENS). Then you could probably to it faster Appending them to a StringBuilder.