Latest .NET 8 Preview 7: time to start final testing

Microsoft has just released .NET 8 Preview 7, the final preview release before the release candidate builds.

At this stage, most new features are close to their final shape, so this is a good point to start more serious upgrade testing.

For an existing C# project, create a test branch and update the target framework:

<TargetFramework>net8.0</TargetFramework>

Then run the normal checks:

dotnet restore
dotnet build
dotnet test

For ASP.NET Core applications, also test the application manually in the same hosting model you use in production.

Good areas to verify:

• authentication
• configuration loading
• logging
• serialization
• background services
• container builds
• deployment scripts.

Tip: test JSON serialization carefully if your application exposes APIs or consumes external JSON payloads. Small serializer behavior changes can be more visible than runtime changes.

If you publish containers, build the image locally:

dotnet publish -c Release

docker build -t myapp-net8-preview .
docker run --rm -p 8080:8080 myapp-net8-preview

Also check the runtime in the container:

docker run --rm myapp-net8-preview dotnet --info

This is a good time to update CI pipelines in a separate branch. Do not wait until the final release before discovering SDK installation, workload, or container image issues.

.NET 8 will be the next LTS release, so teams currently on .NET 6 should pay attention to this release cycle.

The practical goal for Preview 7 is simple: find migration issues before the release candidate and final release arrive.

Breaking changes are listed here. Hope this helps!