How to upgrade from .NET 8 to .NET 9

Migrating from .NET 8 to .NET 9 is a generally straightforward process. You may find below some specific adjustments to make to your projects and libraries when upgrading.

To upgrade to .NET 9:

• First, read What's New in .NET 9
• Install Visual Studio 17.12 Preview 3 or later and run uno.check with the --pre-major parameter to install .NET 9.
• Change all your target framework (TFM) references from net8.0 to net9.0, and net8.0-* to net9.0-*.
• Delete your bin and obj folders

Considerations for WebAssembly

WebAssembly support for .NET 9 has made significant internal changes to use the official .NET SDK. Read the following documentation for WebAssembly migrations.