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 co         


        

Answer 1

The first variant will be best, but only when you are using constant strings.

There are two compilator optimizations (from the C# compiler, not the JIT compiler) that are in effect here. Lets take one example of a program

const string A = "Hello ";
const string B = "World";

...
string test = A + B;

First optimization is constant propagation that will change your code basically into this:

string test = "Hello " + "World";

Then a concatenation of literal strings (as they are now, due to the first optimization) optimization will kick in and change it to

string test = "Hello World";

So if you write any variants of the program shown above, the actual IL will be the same (or at least very similar) due to the optimizations done by the C# compiler.