A constant is a static field whose value can never change.
A constant is evaluated statically at compile time.
A constant can be any of the built-in numeric types, bool, char, string, or an enum type.
A constant is declared with the const keyword and must be initialized with a value.
For example:
public class Test {
public const string Message = "Hello World";
}
A constant is much more restrictive than a static readonly field.
A constant differs from a static readonly field in that the evaluation of the constant occurs at compile time.
For example:
public static double Circumference (double radius) {
return 2 * System.Math.PI * radius;
}
is compiled to:
public static double Circumference (double radius) {
return 6.283 * radius;
}
A static readonly field can have a different value per application.
Constants can also be declared local to a method. For example:
static void Main() {
const double twoPI = 2 * System.Math.PI;
...
}
Non-local constants allow the following modifiers:
| Item | Modifier |
|---|---|
| Access modifiers | public internal private protected |
| Inheritance modifier | new |