api: YAML JSON TOON Database
version: 1.0.0
format: toon
dataset:
  id: 2361
  slug: csharp-dotnet-features
  title: C# and .NET Modern Features
  description: "Modern C# features (C# 8-12) and .NET capabilities: nullable reference types, records, pattern matching, LINQ, async streams, minimal APIs."
  summary: "Modern C# and .NET features with version, description, example and notes: nullable reference types, records, pattern matching, LINQ, async streams, minimal APIs, primary constructors and source generators."
  use_when[2]: You need the C# version that introduced a feature and an idiomatic example.,You are comparing C# idioms with other languages.
  caveats[2]: "Features are tied to language versions, which depend on the .NET SDK; check the project's LangVersion.","Some features, such as source generators, need specific tooling support."
  related[4]: language-comparison-2026,typescript-type-system,behavioral-design-patterns,architectural-design-patterns
  entry_count: 8
  fields[5]{section,field,type,example}:
    features,name,string,Nullable Reference Types
    features,version,string,C# 8.0 / .NET Core 3.0
    features,description,string,Compiler warnings for potential NullReferenceEx…
    features,example,string,string? middleName = null; string firstName = m…
    features,notes,string,Enable with <Nullable>enable</Nullable> in .csp…
  category: Programming Languages
  category_slug: programming-languages
  tags: "csharp,dotnet,nullable-reference-types,records,pattern-matching,linq,async-streams"
  view_count: 53
  created_at: 1778695229
  updated_at: 1778695229
data:
  features[8]{name,version,description,example,notes}:
    Nullable Reference Types,C# 8.0 / .NET Core 3.0,"Compiler warnings for potential NullReferenceException: string? means nullable, string means non-nullable","string? middleName = null; string firstName = middleName ?? \"Unknown\";",Enable with <Nullable>enable</Nullable> in .csproj
    Records,C# 9.0 / .NET 5,"Immutable reference types with value equality, positional syntax, with-expressions for non-mutating updates","public record Person(string FirstName, string LastName); var p2 = p1 with { LastName = \"Smith\" };","Use record class for reference semantics, record struct for value semantics"
    Pattern Matching,C# 8-12,"Type patterns, property patterns, relational patterns, list patterns for expressive conditional logic","return shape switch { Circle c => c.Radius * c.Radius * Math.PI, Rectangle r => r.Width * r.Height, _ => 0 };","Evolves each version: C# 7 (is/switch), C# 8 (property/recursive), C# 10 (extended), C# 12 (list)"
    LINQ,C# 3.0 / .NET Framework 3.5,"Language Integrated Query: declarative data querying with deferred execution, query syntax and method syntax",var adults = people.Where(p => p.Age >= 18).Select(p => p.Name).OrderBy(n => n);,"Works with any IEnumerable<T>; IQueryable<T> for remote execution (EF Core, SQL)"
    Async Streams,C# 8.0 / .NET Core 3.0,"IAsyncEnumerable<T> for asynchronous iteration over sequences, await foreach","await foreach (var item in GetItemsAsync()) { Process(item); }","Essential for paginated APIs, database queries, real-time data streams"
    Minimal APIs,.NET 6,"Simplified HTTP API building without controllers: app.MapGet(\"/\", () => \"Hello\")","var app = WebApplication.Create(args); app.MapGet(\"/todos/{id}\", (int id, TodoDb db) => db.Todos.FindAsync(id));","Reduces boilerplate for small APIs; use for microservices, prototypes, simple backends"
    Primary Constructors,C# 12 / .NET 8,"Constructor parameters directly on class/struct declaration, accessible as instance fields","public class Person(string firstName, string lastName) { public string FullName => $\"{firstName} {lastName}\"; }",Reduces boilerplate; parameters are in scope for the entire class body
    Source Generators,.NET 5 / Roslyn 3.8,"Compile-time code generation: analyze syntax trees and emit new C# source files","[GenerateSerializer] public class MyData { } // Generates serialization code at compile time","Used by System.Text.Json, EF Core, gRPC; eliminates runtime reflection overhead"