Modern .NET development keeps pushing toward simplicity, clarity, and performance. With C# 12+, developers can eliminate noisy constructors, streamline collection handling, and write APIs that feel effortless to maintain. Developers building modern .NET applications with C# 12 gain immediate benefits from clearer syntax and reduced boilerplate.

By adopting features like primary constructors, collection expressions, params collections, and inline arrays, teams routinely cut 30–40% of ceremony out of codebases while keeping enterprise scalability intact.

Why Build Modern .NET Applications with C# 12?

Modern .NET applications with C# 12 allow teams to write cleaner, more efficient code without the structural noise that older C# versions required.

Prerequisites for Building Modern .NET Applications with C# 12

Tools Required

• Visual Studio 2022 or VS Code + C# Dev Kit
• .NET 8 SDK (C# 12)
• .NET 10 SDK (future-ready)

Recommended NuGet Packages

dotnet add package Microsoft.AspNetCore.OpenApi
dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Microsoft.EntityFrameworkCore.SqlServer

Knowledge Required

• Dependency injection
• ASP.NET Core
• LINQ and lambdas
• EF Core basics

Primary Constructors: Transforming Modern .NET Applications with C# 12

Old DI Pattern (Verbose)

public class UserService
{
    private readonly IUserRepository _userRepository;
    private readonly ILogger<UserService> _logger;
    private readonly IEmailService _emailService;

    public UserService(
        IUserRepository userRepository,
        ILogger<UserService> logger,
        IEmailService emailService)
    {
        _userRepository = userRepository;
        _logger = logger;
        _emailService = emailService;
    }

    public async Task CreateUserAsync(string email)
    {
        _logger.LogInformation($"Creating user: {email}");
        await _userRepository.AddAsync(new User { Email = email });
        await _emailService.SendWelcomeEmailAsync(email);
    }
}

Modern Primary Constructor (Clean C# 12)

public class UserService(
    IUserRepository userRepository,
    ILogger<UserService> logger,
    IEmailService emailService)
{
    public async Task<User> CreateUserAsync(string email)
    {
        logger.LogInformation($"Creating user: {email}");

        var user = new User { Email = email };
        await userRepository.AddAsync(user);
        await emailService.SendWelcomeEmailAsync(email);

        return user;
    }

    public Task<User?> GetUserAsync(int id) =>
        userRepository.GetByIdAsync(id);
}

Real Business Logic Example

public class OrderProcessor(
    IOrderRepository orderRepository,
    IPaymentService paymentService,
    ILogger<OrderProcessor> logger)
{
    private const decimal MinimumOrderAmount = 10m;

    public async Task<OrderResult> ProcessOrderAsync(Order order)
    {
        if (order.TotalAmount < MinimumOrderAmount)
        {
            logger.LogWarning(
                $"Order amount {order.TotalAmount} below minimum");
            return OrderResult.Failure("Order amount too low");
        }

        try
        {
            var payment = await paymentService.ChargeAsync(order.TotalAmount);

            if (!payment.IsSuccessful)
            {
                logger.LogError($"Payment failed: {payment.ErrorMessage}");
                return OrderResult.Failure(payment.ErrorMessage);
            }

            order.Status = OrderStatus.Paid;
            await orderRepository.UpdateAsync(order);

            logger.LogInformation($"Order {order.Id} processed successfully");
            return OrderResult.Success(order);
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "Unexpected error processing order");
            return OrderResult.Failure("Unexpected error occurred");
        }
    }
}

Collection Expressions in Modern .NET Applications with C# 12

Old Collection Syntax

int[] numbers = new int[] { 1, 2, 3, 4, 5 };
List<string> names = new List<string> { "Alice", "Bob", "Charlie" };
int[][] jagged = new int[][]
{
    new int[] { 1, 2 },
    new int[] { 3, 4 }
};

Modern C# 12 Syntax

int[] numbers = [1, 2, 3, 4, 5];
List<string> names = ["Alice", "Bob", "Charlie"];
int[][] jagged = [[1, 2], [3, 4]];

Spread Syntax

int[] row0 = [1, 2, 3];
int[] row1 = [4, 5, 6];
int[] row2 = [7, 8, 9];

int[] combined = [..row0, ..row1, ..row2];

Real API Example

public class ProductService(IProductRepository repository)
{
    public async Task<ProductListResponse> GetFeaturedProductsAsync()
    {
        var products = await repository.GetFeaturedAsync();

        return new ProductListResponse
        {
            Products =
            [
                ..products.Select(p => new ProductDto(
                    p.Id, p.Name, p.Price, [..p.Tags]))
            ],
            TotalCount = products.Count,
            Categories = ["Electronics", "Clothing", "Books"]
        };
    }
}

public record ProductDto(int Id, string Name, decimal Price, List<string> Tags);

public record ProductListResponse
{
    public required List<ProductDto> Products { get; init; }
    public required int TotalCount { get; init; }
    public required List<string> Categories { get; init; }
}

Minimal APIs in Modern .NET Applications with C# 12

Old Minimal API

app.MapPost("/users",
    async (CreateUserRequest request, UserService service) =>
{
    var user = await service.CreateUserAsync(request.Email);
    return Results.Created($"/users/{user.Id}", user);
});

Modern Minimal API With Metadata

app.MapPost("/users", async (
    [FromBody] CreateUserRequest request,
    [FromServices] UserService service,
    [FromServices] ILogger<UserService> logger) =>
{
    logger.LogInformation($"Creating user: {request.Email}");

    var user = await service.CreateUserAsync(request.Email);
    return Results.Created($"/users/{user.Id}", user);
})
.WithName("CreateUser")
.WithOpenApi()
.Produces(StatusCodes.Status201Created)
.Produces(StatusCodes.Status400BadRequest);

Inline Arrays (Performance Boost in Modern .NET Applications with C# 12)

[System.Runtime.CompilerServices.InlineArray(10)]
public struct IntBuffer
{
    private int _element0;
}

public class DataProcessor
{
    public void ProcessBatch(ReadOnlySpan<int> data)
    {
        var buffer = new IntBuffer();

        for (int i = 0; i < data.Length && i < 10; i++)
            buffer[i] = data[i];

        foreach (var item in buffer)
            Console.WriteLine(item);
    }
}

Final Thoughts on Modern .NET Applications with C# 12

With C# 12+, enterprise .NET apps benefit from:
✔ Less boilerplate
✔ Cleaner collections
✔ Metadata-rich lambdas
✔ Higher performance

By integrating these language features, teams building modern .NET applications with C# 12 unlock easier code maintenance, faster development, and fewer bugs.