EOPA Data Filters Support - C# UCAST integration for LINQ

Important

The reference documentation for this library is available at https://open-policy-agent.github.io/ucast-linq

Overview

This library allows users to integrate dynamic data filtering rules into LINQ queries that are driven by policies written in Rego.

Below is a high-level sequence diagram of the process:

sequenceDiagram
    C# Application ->>+ OPA: Compile API Request
    OPA ->>- C# Application: UCAST Result

    C# Application ->> C# Application: Translate UCAST to LINQ Query

    participant Database@{ "type" : "database" }
    C# Application ->>+ Database: LINQ Query
    Database ->>- C# Application: Query Results

Loading

See the Development Workflow docs for more details.

Installation

Nuget

dotnet add package OpenPolicyAgent.Ucast.Linq

Example Usage

Let's assume that we have a collection of random integers, and wish to filter them with a LINQ query using multiple criteria:

using System;
using System.Linq;

public record SimpleRecord(int Value);

var numbers = new int[] { -1523, 1894, -456, 789, -1002, 345, -1789, 567, 1234, -890, 123, -1456, 1678, -234, 567, -1890, 901, -345, 1567, -789 };
var collection = numbers.Select(n => new SimpleRecord(n)).ToList();
var results = collection.Where(x => x.Value >= 1500 || (x.Value < 400 && (x.Value > 0 || x.Value < -1500)))
                        .OrderBy(x => x.Value)
                        .ToList();

Console.WriteLine(string.Join("\n", results));

Output

SimpleRecord { Value = -1890 }
SimpleRecord { Value = -1789 }
SimpleRecord { Value = -1523 }
SimpleRecord { Value = 123 }
SimpleRecord { Value = 345 }
SimpleRecord { Value = 1567 }
SimpleRecord { Value = 1678 }
SimpleRecord { Value = 1894 }

Using this library, the same filters can be constructed dynamically using UCAST expressions (which can be deserialized from JSON):

using System;
using System.Linq;
using OpenPolicyAgent.Ucast.Linq;

public record SimpleRecord(int Value);

var conditions = new UCASTNode { Type = "compound", Op = "or", Value = new List<UCASTNode>{
    new UCASTNode { Type = "field", Op = "ge", Field = "r.value", Value = 1500 },
    new UCASTNode { Type = "compound", Op = "and", Value = new List<UCASTNode>{
        new UCASTNode { Type = "field", Op = "lt", Field = "r.value", Value = 400 },
        new UCASTNode { Type = "compound", Op = "or", Value = new List<UCASTNode>{
            new UCASTNode { Type = "field", Op = "gt", Field = "r.value", Value = 0 },
            new UCASTNode { Type = "field", Op = "lt", Field = "r.value", Value = -1500 },
        } },
    } },
} };

var numbers = new int[] { -1523, 1894, -456, 789, -1002, 345, -1789, 567, 1234, -890, 123, -1456, 1678, -234, 567, -1890, 901, -345, 1567, -789 };
var collection = numbers.Select(n => new SimpleRecord(n)).ToList();
var results = collection.AsQueryable()
                        .ApplyUCASTFilter(conditions, new MappingConfiguration<SimpleRecord>(prefix: "r"))
                        .OrderBy(x => x.Value)
                        .ToList();

Console.WriteLine(string.Join("\n", results));

Output

SimpleRecord { Value = -1890 }
SimpleRecord { Value = -1789 }
SimpleRecord { Value = -1523 }
SimpleRecord { Value = 123 }
SimpleRecord { Value = 345 }
SimpleRecord { Value = 1567 }
SimpleRecord { Value = 1678 }
SimpleRecord { Value = 1894 }

Community

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