Question

I have a function of an class in C# that compares one object to another. More or less a Equals function but with some added code. My object has quite a few variables and I would like to compare each and if any are different add them to a data table. Right now my function looks something like:

    public bool compareSysInfo(SystemInfo expected, SystemInfo comp)
    {
        ComparePopup popup = new ComparePopup();
        bool finalResult = true;//initial assumption that they are equal
        //compares branding
        if (expected.branding != comp.branding)
        {
            finalResult = false;
            popup.addDataToTable("Branding", comp.getBranding() + "", expected.getBranding() + "");
        }
        //compares pro #
        if (expected.getPro() != comp.getPro())
        {
            finalResult = false;
            popup.addDataToTable("Pro Number", comp.getPro() + "", expected.getPro() + "");
        }

It continues like that for all the variables. I would like to avoid excessive if statements, is there a way to create a abstract method and use a loop? I looked into delegates but I’m not sure how to use them in this context. Maybe I’m going about this wrong and should do something completely different like adding them to a collections and just using a for loop to compare the objects. I feel like I’m missing something obvious. I know any place that has repetitive code like this you can implement better, it’s just I don’t know how. Any advice here would be great.
Thanks for the help.

Answer 1

Create a strategy class, inherit from it for each rule, and provide your class with a list containing these:

public MyClass {
 readonly IEnumerable<Rule> _rules;
 public MyClass(IEnumerable<Rule> rules) {
    _rules
 }

 public bool CompareSysInfo(SystemInfo expected, SystemInfo comp) {
   // i prefer linq over loops
   var result = from r in _rules
                where !r.CheckRule(expected, comp)
                select false;
   return result.Count() > 0; // only returns true if no rule checks return false
 }
}

Then for each rule check you implement an instance of the Rule class (or interface):

public abstract class Rule {
   protected ComparePopup Popup { get; private set; }
   protected Rule(ComparePopup popup) {
     Popup = popup;
   }
   public abstract bool CheckRule(SystemInfo expected, SystemInfo comp);
}

public class BrandingRule : Rule {

   public BrandingRule(ComparePopup popup) : base(popup) { }

   public override bool CheckRule(SystemInfo expected, SystemInfo comp) {
     var result = expected.branding == comp.branding;
     if(!result)
       Popup.addDataToTable("Branding", comp.getBranding() + "", expected.getBranding() + "");
   }
}

This strategy affords you the ability to add, remove, or modify rules and what they do independently of the code that needs to use them.