Is it better coding practice to define variables outside a foreach even though more verbose?

Question

In the following examples:

• the first seems more verbose but less wasteful of resources
• the second is less verbose bu

Answer 1

I generally declare variables as close to their use as scoping allows, which in this case would be your second example. Resharper tends to encourage this style as well.

Answer 2

I think it depends on what you are trying to solve. I like the second example, because you can move the code in one step. I like the first example, because it is faster due to less stack manipulations, less memory fragmentation, and less object construction/creation.

Answer 3

I'm not sure what you gain by defining the string variable outside of the loop. Strings are immutable so they are not reused. Whenever you assign to them, a new instance is created.

Answer 4

For POD type data declare closest to first use. For anything like a class that does any memory allocation, then you should consider declaring those outside of any loops. Strings will almost certainly do some form of allocation and most implementations (at least in C++) will attempt to reuse memory if possible. Heap based allocations can be very slow indeed.

I once profiled a bit of C++ code that included a class that new'd data in its ctor. With the variable declared outside of the loop it ran 17% faster than with the variable declared inside the loop. YMMV in C# so profile performance you may be very surprised at the results.

Answer 5

This is my favourite part of Linq which I guess it fits here:

names.ForEach(x => Console.WriteLine("{0}1, {0}2, {0}3", x));

Answer 6

Follow a simple rule while declaring variables

Declare it when you need it for the first time