Is this a proper way of defining a rule in NRules?

Question

public class AllowAtleastOneCountryRule : Rule
{
    public override void Define()
    {
        Profile profile = null;

        string str = @"At least one country has to be defined as 'permitted'";


        bool enabled = AllRules.GetDict()[str];//Checks if the rule is enabled


        When()
            .Match<FundProfile>(() => productProfile)
            .Exists<FundProfile>(p => enabled, p => RuleViolation(p));


        Then()
            .Do(_ => profile .DisplayError(str));


    }


    bool RuleViolation(FundProfile pp)
    {
        try
        {


            if (pp.DefaultMode.Equals(Helper.DefaultModes.Allow.ToString()))
            {
                if (pp.ListOfCountries.Count < pp.TotalCountries)//Okay
                    return false;
                else//Rule violation
                    return true;
            }
            else//Deny
            {
                if (pp.ListOfCountries.Count > 0)//Okay
                    return false;
                else//Rule violation
                    return true;
            }

        }
        catch(Exception e)
        {
            throw new InvalidRuleException(e.Message);
        }

    }
}

As you can see I am calling another method with the rule to evaluate few conditions. I feel like I am not using the full functionality of Rete algorithm here as I am pre-evaluating things for my self. Can anyone guide me on how to approach this?

Answer 1

Your code looks good, you have a complex rule and you encapsulate it.

Following the documentation and samples, you could implement an elegant solution.

Implementing complex logic with .Query instead of .Exists, translating your encapsulated logic to a linq or lambda expresion. Then applying DSL Extension, making your code more readable.