Unlock 7 Powerful Object Initialization 2.0 Tricks for 2025

Trick 1: Enforce Essential Properties with `required` Members

The `required` modifier (introduced in C# 11) is a game-changer for ensuring object validity. It solves the age-old problem of forgetting to initialize a critical non-nullable property, which previously could lead to `NullReferenceException` at runtime.

The Old Pain Point

Previously, you'd rely on constructors or nullable reference type warnings (`?`) that could be ignored. An object could be created in an invalid state.

// Old way: Nothing stops a developer from creating an invalid user.
public class User
{
    public string Username { get; set; }
    public string Email { get; set; }
}

var user = new User { Username = "Alex" }; // Oops, Email is null!

The 2.0 Solution: The `required` Keyword

By marking a property as `required`, you shift the responsibility to the developer creating the object. The compiler will issue an error if a `required` property is not set in an object initializer, guaranteeing the object is valid upon creation.

// The modern, safe way
public class User
{
    public required string Username { get; set; }
    public required string Email { get; set; }
}

// COMPILE-TIME ERROR: Required member 'User.Email' must be set.
// var user = new User { Username = "Alex" }; 

// This is the only way to compile, ensuring a valid state.
var validUser = new User { Username = "Alex", Email = "alex@example.com" };

Trick 2: Craft Immutable Objects with `init`-only Setters

Immutability is a core tenet of modern, concurrent programming. `init`-only setters (C# 9) allow you to create objects whose properties can only be set during initialization, making them inherently thread-safe and predictable.

The Old Way: Read-only or Mutable

You either had to set everything in the constructor (which can get verbose) or use public setters, allowing the object's state to be changed at any time.

The 2.0 Solution: `init`

The `init` accessor behaves like a `set` accessor, but it can only be called during object initialization. Once the object is constructed, its properties become effectively read-only.

public class Transaction
{
    public Guid TransactionId { get; init; }
    public decimal Amount { get; init; }
    public DateTime Timestamp { get; init; }

    public Transaction()
    {
        Timestamp = DateTime.UtcNow; // Can be set here
    }
}

var purchase = new Transaction 
{ 
    TransactionId = Guid.NewGuid(), // Allowed during initialization
    Amount = 99.99m
};

// COMPILE-TIME ERROR: 'Transaction.Amount' can only be assigned in an initializer.
// purchase.Amount = 105.50m;

Trick 3: Simplify Syntax with Target-Typed `new` Expressions

While a smaller change, target-typed `new` expressions (C# 9) reduce code verbosity and improve readability, especially when the type is already known from the context.

The Old Redundancy

We often repeated the type name on both sides of the assignment.

Dictionary<string, List<int>> userScores = new Dictionary<string, List<int>>();

The 2.0 Solution: `new()`

When the compiler can infer the type from the left-hand side of an assignment or from a method parameter, you can simply use `new()`.

// Much cleaner!
Dictionary<string, List<int>> userScores = new();

public void ProcessConfig(ConfigOptions options) { /* ... */ }

// Pass a new object without specifying the type again.
ProcessConfig(new() { Timeout = 5000, Retries = 3 });

Trick 4: Non-Destructive Mutation using `with` Expressions

Working with immutable objects raises a question: how do you create a new version with a slight change? The `with` expression (C# 9, enhanced for classes in C# 10) provides an elegant solution for non-destructive mutation, primarily used with `record` types.

The Old Manual Copy

You had to write a copy constructor or a method to manually create a new object, copying all properties and changing just one. This is error-prone and tedious.

The 2.0 Solution: `with`

The `with` expression creates a shallow copy of an object, allowing you to specify which properties should have new values in the new instance.

public record Product(int Id, string Name, decimal Price);

var laptop = new Product(101, "DevBook Pro", 1999.00m);

// Create a new product instance for a sale, keeping the Id and Name.
var laptopOnSale = laptop with { Price = 1799.00m };

// laptop object remains unchanged.
// laptopOnSale is a new object: Product(101, "DevBook Pro", 1799.00m)

Trick 5: Eliminate Boilerplate with Primary Constructors

Primary constructors (C# 12) are the latest evolution in reducing boilerplate code for classes and structs. They allow you to declare constructor parameters directly on the type definition itself.

The Old Constructor Boilerplate

The classic pattern involved declaring private fields and a constructor to assign parameters to those fields—a lot of repetitive code for a simple task.

// Old way: Lots of boilerplate
public class ApiClient
{
    private readonly HttpClient _httpClient;
    private readonly string _apiKey;

    public ApiClient(HttpClient httpClient, string apiKey)
    {
        _httpClient = httpClient;
        _apiKey = apiKey;
    }
}

The 2.0 Solution: Primary Constructors

Now, you can define the parameters right in the class declaration. The parameters are in scope throughout the class body and can be used to initialize properties or fields.

// The C# 12 way: concise and clear
public class ApiClient(HttpClient httpClient, string apiKey)
{
    // Parameters can be used to initialize properties
    public string BaseUrl { get; init; } = httpClient.BaseAddress?.ToString() ?? "";

    public async Task<string> GetDataAsync(string endpoint)
    {
        // Or used directly in methods
        var request = new HttpRequestMessage(HttpMethod.Get, endpoint);
        request.Headers.Add("X-API-Key", apiKey);
        var response = await httpClient.SendAsync(request);
        return await response.Content.ReadAsStringAsync();
    }
}

Trick 6: Unify Collection Creation with Collection Expressions

Another powerful C# 12 feature, collection expressions provide a single, streamlined syntax for creating common collection types like arrays, `List`, and `Span`.

The Old Syntax Fragmentation

Creating different collections required slightly different, and sometimes verbose, syntaxes.

// Old ways
int[] array = new int[] { 1, 2, 3 };
List<int> list = new List<int> { 4, 5, 6 };
Span<int> span = new int[] { 7, 8, 9 };

The 2.0 Solution: `[]` Syntax

The new `[ ... ]` syntax is target-typed, meaning the compiler infers the collection type from the context, creating a unified and concise initialization experience.

// The new, unified way
int[] array = [1, 2, 3];
List<int> list = [4, 5, 6];
Span<int> span = [7, 8, 9];

// Can even use the spread `..` operator
int[] combined = [..array, ..list, ..span]; // [1, 2, 3, 4, 5, 6, 7, 8, 9]

Trick 7: The Ultimate Combo: `required init` for Bulletproof Immutability

The true power of these features shines when you combine them. Using `required` with `init` creates the perfect property: it must be set during initialization, and it cannot be changed afterward. This pattern is the new gold standard for creating robust, immutable Data Transfer Objects (DTOs) and entities.

public class OrderDetailsDto
{
    public required Guid OrderId { get; init; }
    public required string CustomerId { get; init; }
    public required List<OrderItemDto> Items { get; init; }
    public decimal TotalPrice { get; init; }
}

// This object is guaranteed to be fully populated and immutable.
var order = new OrderDetailsDto
{
    OrderId = Guid.NewGuid(),
    CustomerId = "CUST-123",
    Items = [new(ProductId: 99, Quantity: 2)], // Using collection expressions!
    TotalPrice = 150.75m
};

// Any attempt to omit a required property results in a compile error.
// Any attempt to change a property after creation results in a compile error.

Old vs. New: A Quick Comparison

Conclusion: Building Better Objects for 2025

The evolution of object initialization in C# is not just about syntactic sugar. It's a fundamental shift towards writing code that is safer by design. By embracing `required` members, `init`-only setters, primary constructors, and the other tricks outlined here, you can eliminate entire classes of bugs, reduce boilerplate, and make your code's intent crystal clear.

As you build applications for 2025 and beyond, make these powerful features a core part of your development toolkit. Your future self—and your teammates—will thank you for the clean, robust, and highly maintainable objects you create.