RuleEngine

Purpose

This simple rule engine is a .NET Standard library 2.0, which uses Microsoft's DLR DynamicExpressionParser in the background. The goal was to make a simple engine which is easy to use and compatible with many projects.

Use

Instantiating the kernel

The IKernel interface is implemented with Kerner in order to support Inverson Of Control.

IKernel ruleEngine = new Kernel();

Role of the IRule

The engine is designed to use any object as a rule which implements IRule interface in order to make it easy to use with an ORM.

public interface IRule
{
    string Key { get; set; }
    string Expression { get; set; }
}

//...
void AddRule(IRule rule);
//...

Simple Validation

String expressions can be simply against the object passed to the engine.
Creating a fact:

var fact = new Person {Age = 37, Income = 45000, NumberOfChildren = 3};

Validating the fact:

var result = ruleEngine.Validate(fact, "(f.Age > 3 && f.Income > 100000) || f.NumberOfChildren > 5");
// result = false

Validate All

More than one expreession can be added to the engine

var rules = new List<Rule>
{
    new Rule {Key = "1", Expression = "(f.Age > 3 && f.Income < 50000) || f.NumberOfChildren > 2"},
    new Rule {Key = "2", Expression = "(f.Age > 3 && f.Income > 100000) || f.NumberOfChildren > 5"}
};

ruleEngine.AddRules(rules);

// Validate against all rules when no key passed
var result = ruleEngine.ValidateAll(f);
// result = false

// Only validate against rules with the matching key
var result = ruleEngine.ValidateAll(f, "1");
// result = true

Validate Any

The calls are the same as the case of validate all, however it returns true if any case is true.

var rules = new List<Rule>
{
    new Rule {Key = "1", Expression = "(f.Age > 3 && f.Income < 50000) || f.NumberOfChildren > 2"},
    new Rule {Key = "2", Expression = "(f.Age > 3 && f.Income > 100000) || f.NumberOfChildren > 5"}
};

ruleEngine.AddRules(rules);

// Validate against all rules when no key passed
var result = ruleEngine.ValidateAny(f);
// result = true

// Only validate against rules with the matching key
var result = ruleEngine.ValidateAny(f, "1");
// result = true