C# which is right or better expression?

Question

DateTime theMonth = DateTime.Now;
for(int i = 0; i<8; i++){
     string curMonth = theMonth.AddMonths(-i).ToString("MM/yyyy");
}

Or,

DateTime theMonth = DateTime.Now;
string curMonth;
for(int i = 0; i<8; i++){
     curMonth = theMonth.AddMonths(-i).ToString("MM/yyyy");
}

which is right or better expression? Or same?

@recursive sorry I changed code, my question is, is it OK to define variable in loop? — Expert wanna be, Nov 08 '12 at 05:28
One notion of "better" is to use the smallest scope possible for any given variable. So, while this code snippet is too short for real judgment, according to a theory of minimal scope, declaring the variable inside the loop is preferable. — Erik Eidt, Nov 08 '12 at 05:33
http://www.dotnetperls.com/for-foreach might be useful info. — Hardrada, Nov 08 '12 at 06:02
Also another SO answer on this: http://stackoverflow.com/questions/982963/is-there-any-overhead-to-declaring-a-variable-within-a-loop-c/983271#983271 — Hardrada, Nov 08 '12 at 06:05

score 4 · Answer 1 · answered Nov 08 '12 at 06:12

Use

DateTime theMonth = DateTime.Now;
for(int i = 0; i<8; i++){
     string curMonth = theMonth.AddMonths(-i).ToString("MM/yyyy");
}

if you're only going to be using curMonth inside the loop, AND you don't need its value to persist across loop iterations.

Use

DateTime theMonth = DateTime.Now;
string curMonth;
for(int i = 0; i<8; i++){
     curMonth = theMonth.AddMonths(-i).ToString("MM/yyyy");
}

if you're planning on using curMonth after your loop code has finished executing, or you need the value to hold its value between iterations.

score 0 · Answer 2 · answered Nov 08 '12 at 06:09

@recursive sorry I changed code, my question is, is it OK to define variable in loop?

Of course it is ok to define variables in a loop. Just notice that the content of this variable will be lost everytime the loop reaches the end "}". So your initial question can't be answered here because there is no better expression. It depends on your requirements

C# which is right or better expression?

2 Answers2