.NET Conf Local - .NET 9 Breaking Changes

Presentation for the Dot Net North '.NET Conf Local' event in January 2025. An overview of .NET 9 Breaking Changes.

Event Meetup Listing • Presentation Link

DotNet9BreakingChangesDemo (As featured in the Presentation)

Demo Code Link

Demos - turn on or off in Program.cs to showcase - run as .NET 8 vs .NET 9

Core .NET Libraries

• BigIntegerMaximumLength.Example();
• EmptyEnvironmentVariables.Example();
• InlineArrayAttributes.Example();
• ArrayOfTypeVoid.Example();

Serialization

• BinaryFormatterThrows.Example();
• NullableJsonDocument.Example();

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Links from presentation

🎓 Breaking changes in .NET 9 - Microsoft Learn

Core .NET Libraries

• BigInteger maximum length
• Support for empty environment variables
• Default Equals() and GetHashCode() throw for types marked with InlineArrayAttribute
• Creating type of array of System.Void not allowed

Serialization

• BinaryFormatter always throws
• Nullable JsonDocument properties deserialize to JsonValueKind.Null

🚀 Get .NET 9

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