C# 14: Introducing partial constructors and partial events

Introduction

C# 14 introduces a subtle but genuinely useful improvement for developers working with large classes or source-generated code: constructors and events can now be declared as partial. This small change opens the door to cleaner file organisation and more flexible code-generation scenarios.

What this feature enables

Before C# 14, constructors and events always had to live entirely in a single file. If a class was split across multiple partial files, you couldn’t distribute constructor logic the same way you already could with methods. With C# 14, you can now write a partial class and complete the constructor elsewhere

Partial events follow the same pattern:

public partial event EventHandler? Updated;

And their add/remove/invoke logic can be implemented in another file.

Benefits in real-world codebases

• Cleaner separation of generated vs. handwritten code
  Tools can generate part of a constructor, and developers can finish the implementation without touching generated files.
• More modular organisation
  Large classes often end up split by domain concerns. Being able to distribute constructor and event logic across those partial files keeps things consistent.
• Helpful for incremental development
  A constructor can begin as a simple declaration and later gain behaviour in a separate file as the class evolves.

Considerations

• All partial constructor declarations must match exactly: signature, modifiers, and accessibility.
• Partial events behave like regular events; partial only affects file distribution, not runtime semantics.
• Smaller classes may still be clearer when kept in one file.

Conclusion

This feature won’t transform everyday class design, but it adds a welcome layer of flexibility especially for codebases using source generators or splitting large types into multiple files. It’s a small enhancement that smooths out real-world workflows in C# 14.