Modern C# Features (C# 8-12)
Explore the latest C# features that make .NET Core development more efficient and expressive
Module Overview & Professional Context
ASP.NET Core is the web framework built on top of .NET Core, and it is one of the most capable, performant, and production-proven web frameworks available in any programming ecosystem. Rebuilt from scratch alongside .NET Core, ASP.NET Core replaced the monolithic, Windows-only ASP.NET Framework with a modular, cross-platform architecture that runs efficiently on Linux containers, Windows servers, and macOS development machines alike. It powers web APIs, server-rendered web applications, real-time SignalR hubs, gRPC services, and Blazor WebAssembly applications — all within a single, unified framework. The architectural centerpiece of ASP.NET Core is its middleware pipeline. Every HTTP request that arrives at an ASP.NET Core application passes through a linear sequence of middleware components. Each middleware can inspect and modify both the incoming request and the outgoing response, then either pass the request to the next middleware or short-circuit the pipeline by sending a response. This design creates extraordinary flexibility: authentication, authorization, logging, request compression, response caching, static file serving, CORS, and routing are all implemented as middleware components that can be composed in any order. The application's startup code (Program.cs in modern .NET) assembles the middleware pipeline using a series of app.Use() or app.UseXxx() extension method calls. Dependency Injection (DI) is built into ASP.NET Core at the framework level — not as an afterthought or external library, but as a first-class, built-in feature. The IServiceCollection interface accumulates service registrations during application startup, and the IServiceProvider resolves them at runtime. Services can have three lifetimes: singleton (one instance for the entire application lifetime), scoped (one instance per HTTP request), or transient (a new instance every time requested). This built-in DI system eliminates the need for external IoC containers in most projects and encourages the SOLID software design principles — particularly the Dependency Inversion Principle — naturally throughout the codebase. Routing in ASP.NET Core determines which endpoint an incoming request should be handled by. Modern ASP.NET Core uses attribute routing on controllers and actions, or minimal APIs that define routes with lambda handlers directly in Program.cs. The routing system supports route constraints, conventional routes, area-based routing, and route parameter transformation. RESTful API design emerges naturally from the controller-action model with HTTP method attributes like [HttpGet], [HttpPost], [HttpPut], and [HttpDelete] mapping directly to the standard REST verbs.
Skills & Outcomes in This Module
- Deep conceptual understanding with the 'why' behind each feature
- Practical code patterns used in real enterprise codebases
- Common pitfalls, debugging strategies, and professional best practices
- Integration with adjacent technologies and architectural patterns
- Interview preparation: key questions on this topic with detailed answers
- Industry context: where and how these skills are applied professionally
C# 8.0 Features
// Nullable reference types
string? nullableString = null;
string nonNullableString = "Hello";
// Pattern matching enhancements
public static string GetDisplayText(object obj) => obj switch
{
string s when s.Length > 10 => s.Substring(0, 10) + "...",
string s => s,
int i => i.ToString(),
DateTime dt => dt.ToString("yyyy-MM-dd"),
_ => "Unknown"
};
// Using declarations
public void ProcessFile(string path)
{
using var file = File.OpenRead(path);
// File is automatically disposed at end of scope
}
// Static local functions
public void Calculate()
{
static int Add(int a, int b) => a + b;
var result = Add(5, 3);
}C# 9.0 Features
// Records
public record Person(string FirstName, string LastName, int Age);
// Init-only properties
public class Product
{
public string Name { get; init; }
public decimal Price { get; init; }
}
// Pattern matching improvements
public static bool IsValidEmail(string email) => email is not null and not "" and contains "@";
// Target-typed new expressions
List<string> names = new() { "Alice", "Bob", "Charlie" };
Dictionary<string, int> ages = new() { ["Alice"] = 30, ["Bob"] = 25 };