Philiprehberger.IdGenerator

Sortable, URL-safe unique ID generators — ULID, monotonic ULID, NanoID, UUID v7, and prefixed IDs.

Installation

dotnet add package Philiprehberger.IdGenerator

Usage

using Philiprehberger.IdGenerator;

// Generate a ULID (sortable, 26 chars)
var ulid = Id.NewUlid();
Console.WriteLine(ulid); // "01HXYZ..."

// Generate a monotonic ULID — strictly increasing within a millisecond
var mono = Id.NewMonotonicUlid();

// Generate a NanoID (21 chars, URL-safe)
var nano = Id.NewNanoId();
Console.WriteLine(nano); // "V1StGXR8_Z5jdHi6B-myT"

// Generate a NanoID with custom size and alphabet
var custom = Id.NewNanoId(size: 10, alphabet: "0123456789abcdef");

// Generate a Stripe-style prefixed ID
var prefixed = Id.NewPrefixed("usr");
Console.WriteLine(prefixed); // "usr_01HXYZ..."

// Generate a short ID (12 chars)
var shortId = Id.NewShortId();
Console.WriteLine(shortId); // "a8f3kQ_9xZrT"

// Generate a UUID v7 (RFC 9562) — time-sortable Guid
Guid guidV7 = Id.NewGuidV7();

ULID

using Philiprehberger.IdGenerator;

var ulid = new Ulid();

// Extract timestamp
DateTimeOffset timestamp = ulid.Timestamp;

// Parse from string
var parsed = Ulid.Parse("01HXYZ...");

// Safe parsing
if (Ulid.TryParse("01HXYZ...", out var result))
{
    Console.WriteLine(result);
}

// Convert to GUID
Guid guid = ulid.ToGuid();

// Round-trip through raw bytes
byte[] bytes = ulid.ToByteArray();
var restored = Ulid.FromBytes(bytes);

// ULIDs are sortable
var a = Id.NewUlid();
var b = Id.NewUlid();
Console.WriteLine(a < b); // true (a was created first)

Monotonic ULID

using Philiprehberger.IdGenerator;

// Guaranteed to sort strictly after the previous monotonic ULID,
// even when called multiple times within the same millisecond.
var a = Ulid.NewMonotonic();
var b = Ulid.NewMonotonic();
var c = Ulid.NewMonotonic();
Console.WriteLine(a < b && b < c); // true

UUID v7

using Philiprehberger.IdGenerator;

// RFC 9562 UUID v7 — 48-bit Unix-ms timestamp + 74 bits random.
// Sortable as a string, fits anywhere a Guid is expected.
Guid id = Id.NewGuidV7();
Console.WriteLine(id);

Prefixed IDs

using Philiprehberger.IdGenerator;

// Create prefixed IDs for different entity types
var userId = PrefixedId.Create("usr");   // "usr_01HXYZ..."
var orgId = PrefixedId.Create("org");    // "org_01HXYZ..."

// Validate a prefixed ID
bool valid = PrefixedId.Validate("usr_01HXYZ...", "usr"); // true
bool wrong = PrefixedId.Validate("usr_01HXYZ...", "org"); // false

JSON Serialization

using System.Text.Json;
using Philiprehberger.IdGenerator;

var options = new JsonSerializerOptions();
options.Converters.Add(new UlidJsonConverter());

var ulid = Id.NewUlid();
var json = JsonSerializer.Serialize(ulid, options); // "\"01HXYZ...\""
var back = JsonSerializer.Deserialize<Ulid>(json, options);

API

Id (static factory)

Method	Description
NewUlid()	Generate a new ULID
NewMonotonicUlid()	Generate a strictly-increasing ULID (monotonic within a millisecond)
NewNanoId(int size = 21, string? alphabet = null)	Generate a NanoID
NewPrefixed(string prefix)	Generate a prefixed ID
NewShortId(int length = 12)	Generate a short random ID
NewGuidV7()	Generate a UUID v7 Guid (RFC 9562)

Ulid (readonly struct)

Member	Description
Ulid()	Create a new ULID with current timestamp
Ulid.NewMonotonic()	Create a monotonic ULID guaranteed to sort after any previous monotonic value
Ulid.FromBytes(ReadOnlySpan<byte>)	Create a ULID from its 16-byte representation
Timestamp	Extract the timestamp as DateTimeOffset
Parse(string)	Parse a ULID from a 26-char string
TryParse(string?, out Ulid)	Safely parse a ULID string
ToGuid()	Convert to a Guid
ToByteArray()	Return a copy of the 16-byte payload
ToString()	26-char Crockford Base32 representation
==, !=, <, >, <=, >=	Comparison operators

NanoId (static)

Method	Description
Generate(int size = 21, string? alphabet = null)	Generate a random NanoID

PrefixedId (static)

Method	Description
Create(string prefix)	Create a prefixed ID with a ULID suffix
Validate(string id, string expectedPrefix)	Check prefix and ULID validity

UlidJsonConverter

Description
System.Text.Json converter for ULID serialization/deserialization

Development

dotnet build src/Philiprehberger.IdGenerator.csproj --configuration Release
dotnet test tests/Philiprehberger.IdGenerator.Tests/Philiprehberger.IdGenerator.Tests.csproj --configuration Release

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License

MIT