ASP.NET Core API using OpenAPI

Blogs:

Implementing an ASP.NET Core API with .NET 9 and OpenAPI

Add a Swagger UI using a .NET 9 Json OpenAPI file

Implement security headers for an API supporting OpenAPI Swagger UI

Nuget package for OpenAPI

Install-Package Microsoft.AspNetCore.OpenApi -IncludePrerelease

History

• 2026-06-07 Update packages
• 2025-12-01 .NET 10
• 2025-08-01 Updated packages
• 2025-05-09 Updated packages
• 2024-11-24 .NET 9
• 2024-10-20 Improve security, API policy per default
• 2024-10-17 Improve security headers
• 2024-10-12 Updated to .NET 9 RC2
• 2024-09-12 Updated to .NET 9 RC1
• 2024-08-13 Updated to .NET 9 Preview 7

Example of OpenAPI with minimal APIs

https://github.com/martincostello/dotnet-minimal-api-integration-testing

Links

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/minimal-apis/aspnetcore-openapi

https://learn.microsoft.com/en-us/aspnet/core/web-api/action-return-types

https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet9/nuget/v3/index.json

https://github.com/RicoSuter/NSwag

https://damienbod.com/2021/08/30/improving-application-security-in-an-asp-net-core-api-using-http-headers-part-3/

https://swagger.io/

https://swagger.io/specification/

https://github.com/martincostello/aspnetcore-openapi

https://github.com/mikekistler/aspnet-openapi-examples

https://andrewlock.net/major-updates-to-netescapades-aspnetcore-security-headers/