ILSpy 9.x is based on .NET 8.0. All artifacts except the self-contained distribution are built framework-dependent, which means .NET 8.0 or later must be installed prior to starting ILSpy.
New Language Features

Updated pattern detection to Roslyn 4.12

Contributions

Diagramming feature by @h0lg (see #3324)
More WPF-related refactorings by...