GuidOne

Good one: the .NET GUID Generation library behind the project http://guid.one

This library implements the following GUID generation algorithms specified in RFC 4122

• Version 1: Date-time and MAC address GUID
• Version 3: MD5 hash & namespace
• Version 4: Random
• Version 5: SHA-1 hash & namespace

It targets .NET Standard 2.0 for maximum compatibility.

Usage

Generating GUIDs

var guidV1 = Uuid.NewV1(); //Generate a V1 GUID for current time + random node
var guidV3 = Uuid.NewV3(GuidNamespaces.DNS, "guid.one"); //Generate a V3 GUID for a particular domain
var guidV4 = Uuid.NewV4(); //Generate a V4 GUID (random)
var guidV5 = Uuid.NewV5(GuidNamespaces.DNS, "guid.one"); //Generate a V5 GUID for a particular domain

var guid = guidV4.AsGuid(); //Convert to a standard .NET Guid

Inspecting GUIDs

var uuid = new Uuid(Guid.Parse("63b00000-bfde-11d3-b852-290676ece2d7")); // Parse a UUID

var version = uuid.Version;
var variant = uuid.Variant;
var version = uuid.Timestamp; //Only for timebased Guids

Generating V1 Guids with no local conflicts

The timestamp GUIDs can conflict if generated too quickly, the library supports a slower mode of generation that makes sure there's no duplicates (non-distributed!)

var uuid = new Uuid(Guid.Parse("63b00000-bfde-11d3-b852-290676ece2d7")); // Parse a UUID

using (var v1Gen = new UuidV1Generator(generationMode: GenerationMode.NoDuplicates)){
  var unique = v1Gen.NewV1(now, PhysicalAddress.Parse("...")).AsGuid();
}

More information

Visit my blog for a 3-part series that dives into the secret world of GUIDs: https://michael-mckenna.com/what-the-guid.