ND.FW.RulesEngine 1.0.0

NdRulesEngine

A minimal, JSON-configurable rule engine built on top of Microsoft RulesEngine. Rules are pure config — no C# changes needed to add or change a rule.

Install

dotnet add package NdRulesEngine

Concepts

Quick Start

var services = new ServiceCollection();
services.AddNdRulesEngine();
var provider = services.BuildServiceProvider();

var registry = provider.GetRequiredService<INdPluginRegistry>();
registry.ScanAssembly(typeof(Program).Assembly); // discovers [NdPlugin] classes

var engine = provider.GetRequiredService<INdRuleEngine>();
engine.LoadWorkflowFromJson(File.ReadAllText("rules.json"));

var input = new Dictionary<string, object?> { ["phone"] = "+919876543210", ["age"] = 10 };
var results = await engine.ExecuteAsync("CustomerValidation", input);

foreach (var r in results)
    Console.WriteLine($"{r.RuleName}: {(r.IsSuccess ? "PASS" : $"FAIL - {r.ErrorMessage}")}");

Rule JSON

{
  "WorkflowName": "CustomerValidation",
  "Rules": [
    {
      "RuleName": "PhoneRequired",
      "Expression": "input1[\"phone\"] != null && input1[\"phone\"].ToString() != \"\"",
      "ErrorMessage": "Phone is required."
    }
  ]
}

• Use bracket notation — input1["field"] — not dot notation. RulesEngine compiles expressions statically and can't resolve dynamic dot-access at runtime.
• Set "Enabled": false to disable a rule without deleting it.

Plugins (context enrichment)

Plugins run before evaluation to fetch or derive values — not to validate.

[NdPlugin("AgeLookupPlugin")]
public sealed class AgeLookupPlugin : INdContextPlugin
{
    public Task EnrichAsync(IDictionary<string, object?> context, IDictionary<string, object?>? parameters, CancellationToken ct = default)
    {
        context["age"] = 25; // e.g. fetched from an external API
        return Task.CompletedTask;
    }
}

Attach it to a rule in JSON:

{
  "RuleName": "AgeMinimum",
  "Expression": "Convert.ToInt32(input1[\"age\"]) >= 18",
  "ErrorMessage": "Age must be 18 or above.",
  "Plugins": [{ "Name": "AgeLookupPlugin" }]
}

A rule can list multiple plugins; they run in order before the workflow evaluates.

Custom Operators

Any static class can be registered and called by name inside expressions.

public static class Operators
{
    public static bool IsValidPan(object? value) =>
        System.Text.RegularExpressions.Regex.IsMatch(value?.ToString() ?? "", "^[A-Z]{5}[0-9]{4}[A-Z]$");
}

services.AddNdRulesEngine(o => o.CustomOperatorTypes.Add(typeof(Operators)));

{ "RuleName": "PanFormat", "Expression": "Operators.IsValidPan(input1[\"pan\"])", "ErrorMessage": "Invalid PAN." }

Custom operator methods must take object? parameters — RulesEngine passes ExpandoObject values as object?.

API Surface

• INdRuleEngine.LoadWorkflow(NdWorkflowDefinition) / .LoadWorkflowFromJson(string)
• INdRuleEngine.ExecuteAsync(workflowName, input) → IReadOnlyList<NdRuleResult>
• INdPluginRegistry.Register(name, plugin) / .ScanAssembly(assembly)
• NdRuleEngineOptions.CustomOperatorTypes — list of static classes to expose to expressions

License

Internal use.