Andrew Lock • 9/1/2026

The pain of serializing unions and closed class hierarchies with System.Text.Json: Exploring the .NET 11 preview - Part 7

This article examines the new union types and closed class hierarchies introduced in .NET 11 and C# 15, focusing on their serialization with System.Text.Json. The author provides examples of defining unions and closed hierarchies, then attempts to serialize them, encountering various errors and limitations. The post highlights the differences between these type systems, the current pain points in the preview version, and potential improvements expected in future releases. It also touches on deserialization challenges and offers practical insights for developers experimenting with these features.

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#serialization #union types #Systemtextjson