Larsenal Larsenal - 1 month ago 12
C# Question

Does C# optimize the concatenation of string literals?

For instance, does the compiler know to translate

string s = "test " + "this " + "function";


to

string s = "test this function";


and thus avoid the performance hit with the string concatenation?

Answer

Yes. This is guaranteed by the C# specification. It's in section 7.18 (of the C# 3.0 spec):

Whenever an expression fulfills the requirements listed above, the expression is evaluated at compile-time. This is true even if the expression is a sub-expression of a larger expression that contains non-constant constructs.

(The "requirements listed above" including the + operator applied to two constant expressions.)

See also this question.