Question

ReSharper usually suggests me that, and I’m still looking for a good reason of why to do that.

The only thing that came to my mind is that declaring it closer to the scope it will be used, can avoid initializing it in some cases where it isn’t necessary (because a condition, etc.)

Something related with that is the following:

int temp;
foreach (var x in collection) { 
    temp = x.GetValue();
    //Do something with temp
}

Is that really different than

foreach (var x in collection) {
    int temp = x.GetValue();
    //...
}

I mean, isn’t the second code more expensive because it is allocating memory everytime? Or are both the same? Of course, after finished the loop, in the second code the garbage collector will take care about temp variable, but not in the first one…

Answer 1

The cost of the second example is negligible. The only difference is that in the first example, temp will be available outside the scope of the for loop, and thus it will exist longer than if you declared it inside the for loop.

If you don’t need temp outside the for loop, it shouldn’t be declared outside that loop. Like others have said, readability and style are more at play here than performance and memory.