New C# 10 Features You Must Know

The latest evolution of the C# language has finally arrived, bringing a tremendous productivity boost and simplifying the way we write code. With the newest version of the framework, developers are greeted with C# 10, a release focused on reducing boilerplate, enhancing performance, and providing a cleaner synthesis for everyday programming tasks. If you have been following the evolution of this programming language, you will know that the journey towards more concise and expressive code continues stronger than ever. In this article, we will explore the most important new features of C# 10 that every backend software engineer and developer should definitely know.

1. Global Using Directives

One of the most requested features to declutter your project files has finally been implemented. Global using directives allow you to specify using statements that apply across your entire project. Gone are the days of copying and pasting the same set of namespace imports at the top of every single source file.

global using System;
global using System.Collections.Generic;
global using System.Linq;

By defining these in a single file (for instance, a Usings.cs or GlobalUsings.cs file), you instantly clean up your individual classes, improving readability and saving substantial time on large solutions.

2. File-Scoped Namespace Declaration

Indentation matters. With file-scoped namespaces, you no longer need to wrap your entire file content inside a namespace block. This simple yet powerful addition eliminates one level of indentation for all your types, creating horizontally shorter and cleaner code.

namespace MyProject.Services;

public class MyService
{
    // No more mandatory deep indentation!
}

This subtle change heavily influences the visual structure of your files, prioritizing your business logic over structural boilerplate.

3. Record Structs

The previous version of C# introduced records as reference types (classes). C# 10 extends this fantastic feature to value types by introducing record struct. This allows you to combine the value semantics and memory efficiency of structs with the synthesized members (like equality, Deconstruct, and ToString implementations) of records.

• Immutability out of the box: By declaring a readonly record struct, you guarantee thread safety and strict immutability.
• Reduced allocations: Perfect for high-performance scenarios where heap allocation overhead must be minimized.
• Concise syntax: You can define them in a single line, exactly like their class counterparts.

4. Extended Property Patterns

Pattern matching continues to improve dramatically. Before C# 10, nesting property patterns could become excessively wordy and somewhat confusing. Now, C# 10 permite referenciar propiedades anidadas utilizando la notación de punto (dot notation) dentro del propio patrón.

// Before
if (person is { Address: { City: "Seattle" } }) { }

// Now in C# 10
if (person is { Address.City: "Seattle" }) { }

This enhancement simplifies complex object validation and makes conditional logic based on object graphs significantly easier to read and maintain.

5. Constant Interpolated Strings

String interpolation has been a favorite feature since its introduction. However, you could not use interpolated strings for constants—until now. C# 10 permits defining constant strings using interpolation, provided that all the values used in the interpolation are also constants.

public const string BaseUrl = "https://api.example.com/v1";
public const string UsersEndpoint = $"{BaseUrl}/users";

This eliminates the need to use cumbersome + concatenation or static readonly fields when defining configuration keys, paths, or standard messages across your application.

6. Lambda Expression Improvements

Lambda expressions receive substantial upgrades, making them behave more flexibly, similar to traditional local functions. The compiler is now much smarter at inferring their types, meaning you can assign a lambda to a var without explicit cast operators in many cases.

Additionally, you can now define an explicit return type for a lambda, which resolves ambiguities when the lambda can return various types or throws an exception.

Comparative Overview

Frequently Asked Questions (FAQ)

Are record structs mutable by default?

Yes, unlike positional record classes which are immutable by default, positional record structs are mutable. If you want them to be immutable, you must declare them as readonly record struct.

Do global usings affect all files in the solution?

No, global using directives are scoped specifically to the project or assembly where they are defined, not the entire multi-project solution.

Can I combine file-scoped and traditional namespaces?

A single file cannot contain both file-scoped namespaces and traditionally scoped namespaces. You must stick to one style per file.

Conclusion

C# 10 pushes the boundaries of developer productivity even further. By reducing boilerplate with file-scoped namespaces and global usings, and extending advanced features like pattern matching and records, this release cements C# as a premier language for modern software engineering. We highly recommend starting to adopt these features in your projects today to write cleaner, more maintainable code. Keep exploring and happy coding!