Best approach to programming highly complex business/math rules

Question

I have to take a piece of data, and apply a large number of possible variables to it. I really don't like the idea of using a gigantic set of if statements, so i'm looking for help in an approach to simplify, and make it easier to maintain.

As an example:

if (isSoccer)
    val = soccerBaseVal;
else if (isFootball)
    val = footballBaseVal;
.... // 20 different sports

if (isMale)
   val += 1;
else
    val += 5;

switch(dayOfWeek)
{
    case DayOfWeek.Monday:
       val += 12;
    ...
}

etc.. etc.. etc.. with possibly in the range of 100-200 different tests and formula variations.

This just seems like a maintenance nightmare. Any suggestions?

EDIT:

To further add to the problem, many variables are only used in certain situations, so it's more than just a fixed set of logic with different values. The logic itself has to change based on conditions, possibly conditions applied from previous variables (if val > threshold, for instance).

So yes, i agree about using lookups for many of the values, but I also have to have variable logic.

Answer 1

A common way to avoid large switching structures is to put the information into data structures. Create an enumeration SportType and a Dictionary<SportType, Int32> containing the associated values. The you can simply write val += sportTypeScoreMap[sportType] and you are done.

Variations of this pattern will help you in many similar situations.

public enum SportType
{
    Soccer, Football, ...
}

public sealed class Foo
{
    private static readonly IDictionary<SportType, Int32> sportTypeScoreMap =
        new Dictionary<SportType, Int32>
        {
            { Soccer, 30 },
            { Football, 20 },
            ...
        }

    private static readonly IDictionary<DayOfWeek, Int32> dayOfWeekScoreMap =
        new Dictionary<DayOfWeek, Int32>
        {
            { DayOfWeek.Monday, 12 },
            { DayOfWeek.Tuesday, 20 },
            ...
        }

    public Int32 GetScore(SportType sportType, DayOfWeek dayOfWeek)
    {
        return Foo.sportTypeScoreMap[sportType]
             + Foo.dayOfWeekScoreMap[dayOfWeek];
    }
}