How to force a runtime constant to be a compile time constant?

Question

So I am working on a chemistry based project and ran into this tricky problem. I have a bunch of functions doing chemistry type calculations and want to pass avogadros numbe

Answer 1

For a compile-time constant, you need to use the const keyword. But, to use it, your expression itself needs to be a compile-time constant too, as you noticed: you cannot use functions such as Math.Pow.

class Constants
{
    public const double avogadrosNum = 6.022E-22;
}

If you cannot or do not want to rework your constant to a compile-time constant, you cannot use it in compile-time contexts, but you could work around that by overloading, so that a runtime value can be used as sort of a default argument:

class chemCalculations
{
    public double genericCalc() {
        return genericCalc(Constants.avogadrosNum);
    }
    public double genericCalc(double avogadrosNum) {
        // real code here
    }
}

(By the way, the value of the constant is either wrong, or has a highly misleading name. It should most likely be 6.022E+23.)