RulesEngine/docs/index.md

Description

RulesEngine is a highly extensible library to build rule based system using C# expressions

Features

• Json based rules defination
• Multiple input support
• Dynamic object input support
• C# Expression support
• Extending expression via custom class/type injection
• Scoped parameters
• Post rule execution actions

Installation

Nuget package:

Basic Usage

Create a workflow file with rules

[
  {
    "WorkflowName": "Discount",
    "Rules": [
      {
        "RuleName": "GiveDiscount10",
        "Expression": "input1.country == \"india\" AND input1.loyalityFactor <= 2 AND input1.totalPurchasesToDate >= 5000 AND input2.totalOrders > 2 AND input3.noOfVisitsPerMonth > 2"
      },
      {
        "RuleName": "GiveDiscount20",
        "Expression": "input1.country == \"india\" AND input1.loyalityFactor == 3 AND input1.totalPurchasesToDate >= 10000 AND input2.totalOrders > 2 AND input3.noOfVisitsPerMonth > 2"
      }
    ]
  }
] 

Initialise RulesEngine with the workflow:

var workflowRules = //Get list of workflow rules declared in the json
var re = new RulesEngine.RulesEngine(workflowRules, null);

Execute the workflow rules with input:

// Declare input1,input2,input3 
var resultList  = await re.ExecuteAllRulesAsync("Discount", input1,input2,input3);

//Check success for rule
foreach(var result in resultList){
  Console.WriteLine($"Rule - {result.Rule.RuleName}, IsSuccess - {result.IsSuccess}");
}

This will execute all the rules under Discount workflow and return ruleResultTree for all rules

Note: input passed to rulesEngine can be of a concrete type, an anonymous type or dynamic(Expandobject). In case of dynamic object, RulesEngine will internally convert to an anonymous type

Using custom names for inputs

By Default, RulesEngine will name the inputs as input1, input2, input3... respectively. It is possible to use a custom name in rules by passing input as RuleParameter

[
  {
    "WorkflowName": "DiscountWithCustomInputNames",
    "Rules": [
      {
        "RuleName": "GiveDiscount10",
        "Expression": "basicInfo.country == \"india\" AND basicInfo.loyalityFactor <= 2 AND basicInfo.totalPurchasesToDate >= 5000 AND orderInfo.totalOrders > 2 AND telemetryInfo.noOfVisitsPerMonth > 2"
      },
      {
        "RuleName": "GiveDiscount20",
        "Expression": "basicInfo.country == \"india\" AND basicInfo.loyalityFactor == 3 AND basicInfo.totalPurchasesToDate >= 10000 AND orderInfo.totalOrders > 2 AND telemetryInfo.noOfVisitsPerMonth > 2"
      }
    ]
  }
] 

Now we can call rulesEngine with the custom names:

var workflowRules = //Get list of workflow rules declared in the json
var re = new RulesEngine.RulesEngine(workflowRules, null);


// Declare input1,input2,input3 

var rp1 = new RuleParameter("basicInfo",input1);
var rp2 = new RuleParameter("orderInfo", input2);
var rp3 = new RuleParameter("telemetryInfo",input3);

var resultList  = await re.ExecuteAllRulesAsync("DiscountWithCustomInputNames",rp1,rp2,rp3);

ScopedParams

Sometimes Rules can get very long and complex, scopedParams allow users to replace an expression in rule with an alias making it easier to maintain rule.

RulesEngine supports two type of ScopedParams:

• GlobalParams
• LocalParams

GlobalParams

GlobalParams are defined at workflow level and can be used in any rule.

Example

//Rule.json
{
  "WorkflowName": "workflowWithGlobalParam",
  "GlobalParams":[
    {
      "Name":"myglobal1",
      "Expression":"myInput.hello.ToLower()"
    }
  ],
  "Rules":[
    {
      "RuleName": "checkGlobalEqualsHello",
      "Expression":"myglobal1 == \"hello\""
    },
    {
      "RuleName": "checkGlobalEqualsInputHello",
      "Expression":"myInput.hello.ToLower() == myglobal1"
    }
  ]
}

These rules when executed with the below input will return success

  var input = new RuleParameter("myInput",new {
    hello = "HELLO"
  });

  var resultList  = await re.ExecuteAllRulesAsync("workflowWithGlobalParam",rp);