.NET buildpacks now support .NET 10 file-based apps

Change effective on 11 November 2025

We’ve updated our .NET buildpacks to support file-based apps, a .NET 10 feature that allows you to define complete apps in a single *.cs file without project or solution files.

If your app includes a *.sln, *.slnx, *.csproj, *.vbproj, *.fsproj, or *.cs file in the root directory, Heroku automatically recognizes it as a .NET app.

The .NET buildpacks use the following order of precedence to select a build target:

  1. A solution file configured using config vars
  2. A solution file configured using a project.toml file
  3. A single solution file
  4. A single project file
  5. A single C# file-based app

Refer to .NET Behavior in Heroku for more details.