The Open Booking SDK for .NET provides components that aid the implementation of the OpenActive specifications, including the Open Booking API.
A readme is available within the OpenActive.Server.NET library project.
Further documentation, including a step-by-step tutorial, can be found at https://tutorials.openactive.io/open-booking-sdk/.
BookingSystem.AspNetCore provides an example use of the OpenActive.Server.NET library, as a fully standards compliant reference implementation of the OpenActive specifications, including the Open Booking API.
This is designed to have its code copied-and-pasted to provide a quick working starting point for any implementation.
OpenActive.FakeDatabase.NET is an in-memory database that is used by BookingSystem.AspNetCore for illustration purposes. It can be added as a dependency to your project during the initial stages of implementation, to get a conformant test implementation as a starting position.