This morning I decided to write this question: https://stackoverflow.com/questions/11727571/are-there-problems-if-i-have-a-verbose-datatype/11727723#11727723

I don't really explain my scenario about how am I accesing through the nested dictionaries. I decided to have the default alias (IDictionary<string, IDictionary<Levels, IList<Problem>>>) but I'm thinking that's not a good option right now.

I'm gonna show some parts of my code:


public abstract class ProblemBaseFactory : IProblemFactory
    private IDictionary<string, IDictionary<Levels, IList<Problem>>> problemDictionaryPackages;

    protected ProblemBaseFactory()
        problemDictionaryPackages = new Dictionary<string, IDictionary<Levels, IList<Problem>>>();

    protected IDictionary<string, IDictionary<Levels, IList<Problem>>> ProblemDictionaryPackages
        get { return problemDictionaryPackages; }

    public abstract IEnumerable<Levels> AvailableLevels(string packageName);
    public abstract IEnumerable<Problem> LoadProblems(ProblemFactoryProperties properties);


public abstract class RuleProblemFactory : ProblemBaseFactory
    private IDictionary<string, IDictionary<Levels, IList<ProblemRule>>> ruleDictionaryPackages;
    private IRuleAlgorithmSelector ruleAlgorithmSelector;
    private IList<Problem> temp;

    protected RuleProblemFactory()
        : this(new Dictionary<string, IDictionary<Levels, IList<ProblemRule>>>(), new SequentialRuleSelector())

    protected RuleProblemFactory(IRuleAlgorithmSelector ruleAlgorithmSelector)
        : this(new Dictionary<string, IDictionary<Levels, IList<ProblemRule>>>(), ruleAlgorithmSelector)

    protected RuleProblemFactory(IDictionary<string, IDictionary<Levels, IList<ProblemRule>>> ruleDictionary,
        IRuleAlgorithmSelector ruleAlgorithmSelector)
        this.ruleDictionaryPackages = ruleDictionary;
        this.ruleAlgorithmSelector = ruleAlgorithmSelector;


    protected IDictionary<string, IDictionary<Levels, IList<ProblemRule>>> RuleDictionaryPackages
        get { return ruleDictionaryPackages; }

    public override IEnumerable<Problem> LoadProblems(ProblemFactoryProperties properties)
        // does exist the package name?
        if (!ProblemDictionaryPackages.ContainsKey(properties.NamePackage))
            throw new InvalidOperationException("namePackage");

        IDictionary<Levels, IList<Problem>> problemPackage = this.ProblemDictionaryPackages[properties.NamePackage];

        // does exist the list
        if (!problemPackage.ContainsKey(properties.Difficulty))
            problemPackage.Add(properties.Difficulty, new List<Problem>());

        temp = problemPackage[properties.Difficulty];

        if (temp.Count >= properties.Quantity)
            return temp;
            return GenerateProblems(properties);

    private IEnumerable<Problem> GenerateProblems(ProblemFactoryProperties properties)

        ruleAlgorithmSelector.Rules = ruleDictionaryPackages[properties.NamePackage][properties.Difficulty];


    public override IEnumerable<Levels> AvailableLevels(string name)
        return ruleDictionaryPackages[name].Keys;

Sometimes I guess is difficult to readability. What do you recomend me to to mantain a better readability?

  • 1
    \$\begingroup\$ For readabilitiy I prefer the curly brackets in conditions and loops, one place I saw you could use var. I dont mind the nested IDictionary's, if you did wrap them up in another class would that abstraction yield any benefit in your scenario? \$\endgroup\$
    – Jeremy Thompson
    Jul 30, 2012 at 22:56

1 Answer 1


IDictionary<string, IDictionary<Levels, IList<ProblemRule>>> is difficult to understand and maintain. I don't know enough about your problem domain to give you reasonably sounding names for classes, but I'll try.

In your LoadProblems method, I see you set the IDictionary<Levels, IList<ProblemRule>> to a variable named problemPackage, so I would create a class ProblemPackage, containing a list of ProblemRules per Level (I would drop the 's' in Levels) and move the related logic there.

In ProblemBaseFactory you end up with a IDictionary<string, ProblemPackage>. ProblemPackage will have a IDictionary<Level, ProblemRules> and the class ProblemRules will be an easy wrapper around a IList<ProblemRule>.

If you try to delegate the work to these classes, the readability will almost certainly go up.


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