Enterprise C#: How to Write Code You Won't Be Ashamed to Show at Code Review

Enterprise C#: Why Code for a Bank and Code for a Pet Project Are Two Different Universes

If you've ever moved from a small web studio to a large corporation or fintech company, you know that feeling of mild culture shock. Yesterday you could commit a "hotfix" without tests and with a single comment //TODO: refactor, and today you receive a review with 20 comments where every public method requires XML documentation and every dependency needs to be registered in a DI container.

Enterprise C# development isn't about "doing it fast," but about "doing it so it doesn't break three years from now when the original author has already been fired." It's about predictability, scalability, and endless code reviews. Let's break down what enterprise C# development actually consists of and how not to get fired in your first week.

1. Architecture: SOLID Is Not a Buzzword, It's the Law

In a startup, you can get away with a monolith using "magic" strings and giant 2000-line classes. In enterprise, you cannot. Here, every SOLID principle is not an abstraction but a guide to action.

Single Responsibility Principle (SRP)

Your class should not know how to send emails, save to the database, and parse XML all at once. If you see three or more "responsibilities" in one class, that's a code smell. In enterprise, such code will be rejected during code review with the comment "SRP violation, rewrite." Example of bad code:

public class OrderService\n{\n    public void ProcessOrder(Order order)\n    {\n        // 1. Validation\n        // 2. Save to DB\n        // 3. Send email\n        // 4. Logging\n    }\n}

The correct approach is to split it into separate services and use the Mediator or Pipeline pattern:

public class ProcessOrderCommandHandler : IRequestHandler<ProcessOrderCommand, bool>\n{\n    private readonly IOrderRepository _repo;\n    private readonly IEmailService _email;\n    private readonly ILogger<ProcessOrderCommandHandler> _logger;\n\n    public ProcessOrderCommandHandler(IOrderRepository repo, IEmailService email, ILogger<ProcessOrderCommandHandler> logger)\n    {\n        _repo = repo;\n        _email = email;\n        _logger = logger;\n    }\n\n    public async Task<bool> Handle(ProcessOrderCommand request, CancellationToken cancellationToken)\n    {\n        var order = await _repo.GetByIdAsync(request.OrderId);\n        // logic\n        await _email.SendAsync(order.CustomerEmail, "Order processed");\n        _logger.LogInformation("Order {Id} processed", order.Id);\n        return true;\n    }\n}

Notice: each service does exactly one thing. Testing such code is much easier.

2. Dependency Injection — Your Best Friend

In enterprise C# projects, you will almost never see new MyService() inside a class. Instead, you'll use a DI container (usually Autofac or the built-in Microsoft.Extensions.DependencyInjection).

The rule is simple: if a class creates its own dependencies, it violates the Dependency Inversion Principle. In enterprise, this is considered an architectural error. Example:

// ❌ Bad: tight coupling\npublic class ReportGenerator\n{\n    private readonly PdfExporter _exporter = new PdfExporter();\n    public byte[] Generate() => _exporter.Export();\n}\n\n// ✅ Good: dependency inversion\npublic class ReportGenerator\n{\n    private readonly IExporter _exporter;\n    public ReportGenerator(IExporter exporter) => _exporter = exporter;\n    public byte[] Generate() => _exporter.Export();\n}

Registration in startup:

services.AddScoped<IExporter, PdfExporter>();\nservices.AddScoped<ReportGenerator>();

Why is this needed? First, for testing: you can mock IExporter and not gen