JsonRuleEngine.Net 1.0.15

JsonRuleEngine.Net

A simple C# rule engine parser and evaluator using a simple json format. This lib is inspired by the json rules engine. (https://github.com/cachecontrol/json-rules-engine)[https://github.com/cachecontrol/json-rules-engine]

Purpose

In some case you'll need to store some complex conditions object in database. The purpose of this library is to provide a simple way to store and transform to linq Expression tree nested conditional rules stored in json in database, filesystem...

Json format of queries

Here is a basic JSON sample that represents rules

{
  "separator": "And",
  "rules": [
    {
      "separator": "Or",
      "rules": [
        {
          "field": "Name",
          "operator": "equal",
          "value": "Assassin's creed"
        },
        {
          "field": "Name",
          "operator": "equal",
          "value": "Data"
        }
      ]
    },
    {
      "field": "Category",
      "operator": "in",
      "value": [
        "Action",
        "Adventure"
      ]
    },
    {
      "field": "Price",
      "operator": "greaterThan",
      "value": 5
    }
  ]
}

You can post it to a simple controller using the ConditionRuleSet class

[HttpPost]
public IActionResult PostRules([FromBody] ConditionRuleSet rules) {
    // Save it in DB or whatever
    if (ModelState.IsValid) {
	    _db.Add(rules);
	    _db.SaveChanges();
    }
}

Simple use

Installation

You need to install the nuget library

install-package JsonRuleEngine.Net

For evaluating a rule with a single object

string ruleJson = "{  
    \"field\": \"Name\",
    \"operator\": \"equal\",
    \"value\": \"Assassin's creed\" 
}";

Game objectToTest = new Game() { 
    Name = "Assassin's creed"
};

bool result = JsonRuleEngine.Evaluate(objectToTest, ruleJson);

return result; // this must display "True"

For filtering a list using an expression

The expression parsed will work with LinqToSql query with EntityFramework Core.

string ruleJson = "{}"
var expression = JsonRuleEngine.ParseExpression<Game>(ruleJson);
var datas = new List<Game>() {
    new Game() {
        Name = "test"
    }
};

// Works with LinqToSql queries
var list = datas.Where(expression).ToList();

The nested rules object

ConditionRuleSet