Is there any performance gain by declaring an object outside the loop

Question

I have a code where I'm declaring an object inside a loop, like:

foreach(...)
{
ClassA clA = new ClassA();
clA.item1=1;
clA.item2=2;
ClassB.Add(clA);
}

Will there be any performance gain if I modify the code as follows:

ClassA clA;
foreach(...)
{
clA = new ClassA();
clA.item1=1;
clA.item2=2;
ClassB.Add(clA);
}

Thanks in advance.

Answer 1

There is no performance gain as such. It only helps the variable to go out of scope later than sooner.

Answer 2

The compiler will automatically optimize the code to move the declaration outside the loop anyway, so there is nothing to gain by doing this.

For example

while(...){
  int i = 5;
  ...
}

Will be optimized be the compiler into this

int i;
while(...){
  i = 5;
  ...
}

Answer 3

The actual object allocation happens with clA = new ClassA(); so unless you can move it out of the loop you won't get any performance gain.

Answer 4

As everyone's said, not really, but I'd still change your code to:

foreach(...)
{
ClassB.Add(new ClassA() { item1=1, item2=2 });
}