As soon as I started programming C# (ASP.NET) I was surprised at how restrictive constants were. So far, I haven't used them much and I feel I missed the concept. How would you guys make use of constants in a typical ASP.NET application?
How would declare a constant struct such as System.Drawing.Color?
Would you guys use readonly when const cannot be used?
I would like to find out how people are using const and readonly and to discuss alternatives if any.
Constants are for defining things in your program that should not change, but need to be referenced multiple times.
const int SLEEP_TIME = 500; //500 MS = .5 Seconds
//Do Something
Thread.Sleep(SLEEP_TIME);
//Do Something else
Thread.Sleep(SLEEP_TIME);
//Do yet another something.
Now if you want to change SLEEP_TIME you can do it in one place.
As for a constant struct I'd usually use an enum
enum State
{
Stopped = 0,
Running = 1,
Paused = 2
}
Readonly is useful for references that need to be assigned once
private static readonly Logger = new TextLogger();
And if you need to change something (ie: initialize something to null, then change it), it by definition can't be const.
Just from my experience, I've found that a lot of things that I think are constant, really aren't. I end up using a lot of external settings files to hold the information in (who wants to recompile a site if a color changes?)
That said, I've found constants REALLY good for working with array indexes. It helps clarify their intent. For example...
//not readable - variable names don't help either
string a = (string)source[0];
int b = (int)source[1];
bool c = (bool)source[2];
Or the same thing with constants...
const int 0 = NAME_COLUMN;
const int 1 = AGE_COLUMN;
const int 2 = IS_ADMIN_COLUMN;
//even with bad variable names, we know what they are
string a = (string)source[NAME_COLUMN];
int b = (int)source[AGE_COLUMN];
bool c = (bool)source[IS_ADMIN_COLUMN];
