C# 14 new features

In November 2025, Microsoft released C# 14.
It continues the trend of incremental but powerful language improvements. This version focuses on expressiveness, library authoring, and reducing boilerplate, while also adding a few long-requested features.

In this post, we’ll explore the main C# 14 features with clear explanations and practical code samples.

1. Extension Members

C# 14 introduces extension members, allowing extension methods, properties, and other members to be grouped more naturally and behave more like real members.

2. Null-Conditional Assignment

You can now assign values using the null-conditional operator (?.).
The assignment only occurs if the receiver is not null.

3. nameof Supports Unbound Generic Types

nameof can now be used with unbound generic types, which is especially useful for logging, diagnostics, and analyzers.

4. More Implicit Conversions for Span<T> and ReadOnlySpan<T>

C# 14 expands implicit conversions, making Span<T> and ReadOnlySpan<T> even easier to work with.

5. Modifiers on Simple Lambda Parameters

You can now apply modifiers such as ref, out, in, or scoped directly to simple lambda parameters.

6. Field-Backed Properties

C# 14 introduces field-backed properties, eliminating the need for explicit backing fields in many scenarios.

7. Partial Events and Constructors

Just like methods and properties, events and constructors can now be declared as partial.

8. User-Defined Compound Assignment Operators

Types can now define compound assignment operators such as +=, -=, *=, and more.

9. New Preprocessor Directives for File-Based Apps

File-based apps are programs that you compile and run by using dotnet run Program.cs (or any *.cs file). The C# compiler ignores these preprocessor directives, but the build system parses them to produce the output. These directives generate warnings when encountered in a project-based compilation.

The C# compiler ignores any preprocessor directive that starts with #: or #!.

The #! preprocessor directive enables Unix shells to directly execute a C# file by using dotnet run

Conclusion

C# 14 may look subtle at first glance, but it delivers meaningful improvements for everyday development and advanced library scenarios. From extension members and field-backed properties to better Span support and partial events, these features reduce boilerplate and unlock cleaner designs.

If you’re building libraries, analyzers, or performance-sensitive code, C# 14 is well worth exploring.