Rule Evaluation and Object Inheritance

The Code Effects business rules engine supports evaluating descendant source object. To illustrate this concept, create one base class and two classes that inherit from it:

using System;

public class MyBase
{
	public int ID { get; set; } = 0;
	public string Name { get; set; }

	public MyBase() { }
}

public class MySourceOne : MyBase
{
	public DateTime Date { get; set; } = DateTime.MinValue;

	public MySourceOne() { }
}
public class MySourceTwo : MyBase
{
	public TimeSpan Time { get; set; } = TimeSpan.MinValue;

	public MySourceTwo() { }
}

Assume we also have an evaluation type rule that uses only the base class’ fields, like this:

Check if ID is greater than 0 and Name starts with A

If we define instances of all three classes, the Evaluator can evaluate each instance against this rule because it relies solely on fields declared in the base class, and those fields are available to all of its descendants:

using CodeEffects.Rule.Engine;

var zero = new MyBase { ID = 0, Name = "abc" };
var one = new MySourceOne { ID = 1, Name = "xyz" };
var two = new MySourceTwo { ID = 2, Name = "abc" };

// Retrieve Rule XML from your storage
string ruleXml = GetRuleXmlFromSomewhere();

var evaluator = new Evaluator(typeof(MyBase), ruleXml);

bool success = evaluator.Evaluate(zero); // Returns False
success = evaluator.Evaluate(one);       // Returns False
success = evaluator.Evaluate(two);       // Returns True

Notice that we created an instance of the Evaluator using the base type, yet we were able to pass instances of all three classes for evaluation without any exceptions.

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