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Sequential GUIDs with .NET 9

Sequential GUIDs (Globally Unique Identifiers) are a specific type of GUID that are optimized for scenarios where insertion order matters, especially in databases. Traditional GUIDs are randomly generated and can cause performance issues in systems where GUIDs are used as primary keys due to their lack of natural order.

Sequential GUIDs address this problem by maintaining some level of order, making them more efficient for certain use cases. Before .NET 9 I typically had 2 approaches to generate a sequential guid:

  • I let the database generate the sequential guid for me through the NEWSEQUENTIALID function:
  • I generate the id myself using a library like RT.Comb:

Starting from .NET 9 I have a new option to add to my list as the Guid class got a new method Guid.CreateVersion7(),  that returns sequential Guids, according to version 7 UUID RFC 9562. This means that they can be ordered and used as a database table primary key, for example, because the values won't be scattered.

Remark: If no DateTimeOffset is supplied,CreateVersion7() uses DateTimeOffet.UtcNow by default.

More information

Avoiding index fragmentation with sequential guids

Using GuidCOMB in SQL Server and PostgreSQL

NEWSEQUENTIALID (Transact-SQL) - SQL Server | Microsoft Learn

GitHub - richardtallent/RT.Comb: Creating sequential GUIDs in C# for MSSQL or PostgreSql

Guid.CreateVersion7 Method (System) | Microsoft Learn

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