Performance difference in loop

Question

Possible Duplicate:
Difference between declaring variables before or in loop?

Is there any (or any notable) performance difference when I write for example something like this (consider loading tens or hundreds of thousands rows from DB into the collection of Foo objects):

...
Foo myFoo;

while(reader.Read())
{
    myFoo = new Foo();
    myFoo.SomeProperty = reader.GetValue(0);
    ...
    fooCollection.Add(myFoo);
}

or this

...

while(reader.Read())
{
    Foo myFoo = new Foo();
    myFoo.SomeProperty = reader.GetValue(0);
    ...
    fooCollection.Add(myFoo);
}

Duplicate - http://stackoverflow.com/questions/407255/difference-between-declaring-variables-before-or-in-loop — ChrisF, Jan 13 '10 at 10:58
Only sure way to find out is to write some code and time it. — High Performance Mark, Jan 13 '10 at 11:09

score 4 · Answer 1 · answered Jan 13 '10 at 10:59

4

You're creating a new instance of Foo in each iteration of the loop in both snippets so I wouldn't expect to see a difference.

You should profile your code though, using a tool like eqatec profiler:

http://www.eqatec.com/tools/profiler

answered Jan 13 '10 at 10:59

Charlie

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score 2 · Accepted Answer · edited May 23 '17 at 11:47

2

Actually the compiler will generate the same IL in each instance.

See similar questions here and here.

edited May 23 '17 at 11:47

Community

1
1

answered Jan 13 '10 at 11:17

Winston Smith

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Performance difference in loop

2 Answers2