C# in 2025: New Features in Practice

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C# in 2025: What's New in Practice?

The .NET world does not stand still. In 2025, the C# language continues to actively evolve, offering developers tools for writing more concise, safe, and performant code. Each platform update makes everyday development more convenient, and new language constructs allow you to eliminate boilerplate code.

In this article, we will break down three key innovations in C# in 2025 that you can start using right now. All code examples are taken from real practice and adapted for the educational portal pythonlib.ru.

1. Primary Constructors

One of the most anticipated innovations is primary constructors for classes and structs. Previously, this feature was only available for records (record). Now you can declare constructor parameters directly in the class header, which significantly reduces the amount of code.

Let's look at a classic example of creating a user model:

Before (C# 12 and earlier):

public class User{    public string Name { get; }    public int Age { get; }

    public User(string name, int age)    {        Name = name;        Age = age;    }}

Now (C# 2025):

public class User(string name, int age){    public string Name { get; } = name;    public int Age { get; } = age;        public string Greeting => $"Hello, {Name}! You are {Age} years old.";}

As you can see, the code is cleaner. The name and age parameters are now available throughout the class body. This is especially convenient when working with Dependency Injection (DI) in ASP.NET Core:

public class WeatherService(HttpClient httpClient, ILogger<WeatherService> logger){    public async Task<string> GetWeatherAsync(string city)    {        logger.LogInformation("Requesting weather for city {City}", city);        var response = await httpClient.GetStringAsync($"https://api.weather.com/{city}");        return response;    }}

Primary constructors allow you to eliminate many fields and explicit assignments, making the code more declarative.

2. New-Style Collections (Collection Expressions)

In 2025, C# received a powerful update for working with collections. Now you can initialize lists, arrays, and even Span<T> with a unified syntax — collection expressions.

The new syntax uses square brackets [] instead of curly braces {} or new List<T>():

Example of initializing various collections:

// Arrayint[] numbers = [1, 2, 3, 4, 5];

// ListList<string> names = ["Anna", "Boris", "Victor"];

// Span (works without allocations)Span<char> letters = ['A', 'B', 'C'];

The main feature is the spread operator ... It allows you to combine collections without calling .Concat() or .AddRange():

int[] first = [1, 2, 3];int[] second = [4, 5, 6];

// Combining arraysint[] combined = [..first, ..second]; // [1, 2, 3, 4, 5, 6]

// Adding elements to the beginning and endint[] extended = [0, ..combined, 7]; // [0, 1, 2, 3, 4, 5, 6, 7]

This syntax works not only with arrays, but also with List<T>, HashSet<T>, and even custom collections implementing ICollection<T>. For developers accustomed to Python, this approach will feel very familiar and intuitive.