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Day 03Sprint 1 • C# 12 Core
2 Hours

Day 3: C# 12 Records, Structs, Immutability & Value Equality

Traditional classes in C# compare by reference (memory address). Records introduce built-in value-based equality, concise primary constructors, and immutability by default, making them the gold standard for Data Transfer Objects (DTOs), event payloads, and API contracts.

Understand why modern enterprise C# prefers records over traditional DTO classes
Learn positional record syntax with automatic value-based equality
Utilize non-destructive mutation with the with expression
Distinguish class vs record class vs record struct
💡 Simple English Theory of .NET

What is this in Simple, Everyday English?

Traditional classes in C# compare by reference (memory address). Records introduce built-in value-based equality, concise primary constructors, and immutability by default, making them the gold standard for Data Transfer Objects (DTOs), event payloads, and API contracts.

⚙️ Under The Hood: How .NET Executes This Code

Ever wondered what happens behind the scenes when you run dotnet run? Here is the step-by-step internal workflow:

11. Roslyn C# Compiler: Takes your readable C# code and compiles it into MSIL (Microsoft Intermediate Language) bytecode.
22. Common Language Runtime (CLR): The virtual machine environment that loads your assembly (.dll) and manages memory safely.
33. RyuJIT (Just-In-Time) Compiler: Compiles IL bytecode into native 64-bit machine CPU instructions right before execution.
44. Automatic Garbage Collector (GC): Automatically tracks and cleans up objects in RAM (Gen 0, 1, 2) with zero manual memory leaks.

🎯 Core Key Points to Master

  • public record Person(string Name, int Age); creates an immutable type in 1 line
  • Two separate record instances with identical data are considered equal (== returns true)
  • The with operator allows cloning an object while modifying select properties
  • readonly struct provides maximum memory performance with zero heap allocation

💡 Real-World Developer Analogy

A class is like an ID card (identity matters, two twins with identical looks have different IDs). A record is like a ₹500 banknote (value matters: any two ₹500 notes with identical value are interchangeable).

🏢 Why Companies & Tech Giants Use This in .NET

.NET is trusted by high-scale companies like Microsoft, Stack Overflow, and banking institutions because it combines lightning-fast execution speed with strict compile-time type safety and cross-platform Docker cloud deployment.

⚠️ Beginner Trap to Avoid

Avoid blocking asynchronous Tasks with .Result or .Wait() — always use 'await' all the way down to avoid thread pool starvation and freezing your application.

Day 2: C# Type System, Nullable Types & Pattern MatchingDay 4: Object-Oriented Principles, Interfaces & Dependency Inversion