Latest .NET Core 3.0 is now available

Microsoft has just released .NET Core 3.0, the next major version of the cross-platform .NET runtime.

For ASP.NET Core developers, this is an important release because it continues the move away from classic .NET Framework application hosting and toward the newer cross-platform runtime. This means better support for Linux especially, in addition to Windows and macOS.

To test these new features, create an application. You need to have the .NET 3.0 SDK installed, naturally. You can check the installed SDKs with:

dotnet --list-sdks

After installing the .NET Core 3.0 SDK, create a new web application:

dotnet new webapp -n NetCore30WebAppTest
cd NetCore30WebAppTest
dotnet run

The application starts locally, usually on https://localhost:5001 and http://localhost:5000.

One practical change in this release is that Visual Studio 2019 16.3 is the matching Visual Studio version for .NET Core 3.0 development. Make sure you have the update installed.

.NET Core 3.0 also includes C# 8.0, which brings useful language features such as nullable reference types and asynchronous streams.

For Windows developers, another notable part of .NET Core 3.0 is support for Windows desktop applications with WinForms and WPF.

Tip: do not upgrade production applications blindly. Create a test branch, install the SDK, and run the existing test suite first.

For an existing project, check the target framework in the project file:

<TargetFramework>netcoreapp3.0</TargetFramework>

This is also a good time to review old dependencies. Some packages that worked with .NET Core 2.x may need updates before moving to 3.0.

For new ASP.NET Core applications, .NET Core 3.0 is now the natural baseline. For existing systems, plan the upgrade carefully and test hosting, authentication, logging, and deployment scripts.