TheNoobs.ValueObjects.ExternalId

A lightweight and opinionated .NET library that implements Value Objects for external identifiers, using Hashids.net as the generation engine.

Why use ExternalId as a Value Object?

Using raw strings or GUIDs for external IDs exposes your domain to Primitive Obsession. This library solves this by offering:

• Type Safety: Prevents accidental swapping of different ID types (e.g., passing an OrderId where a CustomerId is expected).
• Immutability: Once created, the identifier cannot be changed, ensuring object integrity throughout its lifecycle.
• Smart Obfuscation: Powered by Hashids, your internal (sequential) IDs are not directly exposed, making scraping or enumeration attacks significantly harder.
• Clear Semantics: The use of prefixes makes identifiers human-readable and easily identifiable across external systems (e.g., user_3p98Xz).

Installation

Install via NuGet Package Manager:

dotnet add package TheNoobs.ValueObjects.ExternalId

How to Use

1. Defining your Domain ID

Create a class that inherits from ExternalId. The implementation requires two constructors to cover both generation and hydration scenarios:

public class StubId : ExternalId
{
    // Constructor for hydration (e.g., from Database or external API)
    // It intentionally skips structure validation to allow flexibility when loading existing data.
    public StubId(string value) : base(value)
    {
    }

    // Constructor for generating new IDs
    // Defines the length (e.g., 30 characters) and the identifying prefix.
    public StubId() : base(30, "stub_")
    {
    }
}

2. Practical Examples

// Generating a new unique ID using the Hashids engine
var newId = new StubId();
Console.WriteLine(newId.Value); // Output: stub_... (generated id)

// Hydrating an object from a known string
var existingId = new StubId("stub_abc123");

// Equality comparison (Value-based)
if (newId == existingId)
{
    // ...
}

Design and Persistence

This implementation was designed to be ORM-friendly. The constructor that accepts a string allows Entity Framework or Dapper to reconstruct the object from the database without triggering the hash generation logic, preserving the original value transparently.

License

This project is licensed under the MIT License.

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Developed with love <3 by The Noobs.