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Part II: Types, Memory, and Core Language Internals

Part II of the C# Mastery Guide delves into the core types and memory management principles that underpin C# programming. This section provides a deep understanding of how types are defined, how memory is managed, and the intricacies of the Common Type System (CTS) and the Common Language Runtime (CLR).

Table of Contents

3. The Common Type System (CTS): Values, References, and Memory Layout

• 3.1. The Stack and the Heap: A definitive guide to where your data lives. Exploring method calls, stack frames, and object allocation strategies.
• 3.2. Value Types (struct): In-depth analysis of their memory layout, storage implications on the stack or inline within objects, and performance characteristics.
• 3.3. Reference Types (class): Understanding object headers (Method Table Pointer, Sync Block), and how object references are stored on the stack or within other objects.
• 3.4. The Great Unification: System.Object and Boxing: How value types can be implicitly or explicitly converted to objects (boxing) and the associated performance cost of boxing and unboxing.
• 3.5. Scope and Lifetime: Differentiating lexical scope in C# (compile-time visibility) from object lifetime managed by the Garbage Collector (runtime memory management).
• 3.6. Default Values and the default Keyword: Understanding the default initialization values for built-in types (e.g., int to 0, bool to false, reference types to null), and the default keyword for obtaining these values for any type.

4. Memory Management and Garbage Collection

• 4.1. The .NET Generational Garbage Collector: How the tracing GC works. Detailed explanation of Generations 0, 1, and 2, and the mark-and-compact algorithm.
• 4.2. The Large Object Heap (LOH): Understanding why large objects (arrays, strings) are treated differently, their allocation patterns, and the problem of fragmentation on the LOH.
• 4.3. Finalization and IDisposable: The Dispose pattern for deterministic cleanup of unmanaged resources vs. non-deterministic finalizers. Covers using statements, using declarations (C# 8), and await using for IAsyncDisposable (C# 8).
• 4.4. Weak References: Using WeakReference<T> for scenarios like caching, preventing strong references from hindering garbage collection, and avoiding memory leaks.
• 4.5. Advanced GC: Deep dive into Workstation vs. Server GC modes, concurrent collection, and tuning the GC behavior with GCSettings for specific application needs.

5. Assemblies, Type Loading, and Metadata

• 5.1. Assembly Loading: How the CLR resolves, locates, and loads assemblies during runtime, including the role of AssemblyLoadContext for isolation.
• 5.2. Organizing Code: Namespaces, File-Scoped Namespaces (C# 10), and Global Usings (C# 10): How namespaces function as a compile-time construct, the benefits of file-scoped namespaces for conciseness, and the impact of global usings on project-wide imports.
• 5.3. Reflection and Metadata: Reading and manipulating type information at runtime using System.Reflection. Understanding the performance cost and the immense power of late binding.
• 5.4. Dynamic Code Generation with System.Reflection.Emit: Emitting Common Intermediate Language (IL) at runtime to dynamically create types, methods, and assemblies.
• 5.5. Runtime Type Handles and Type Identity: Understanding the internal representation and significance of RuntimeTypeHandle, RuntimeMethodHandle, and RuntimeFieldHandle for unique type and member identification.
• 5.6. Attributes: Metadata for Control and Information Common Usage and Core Behaviors: A deep dive into frequently used built-in attributes (e.g., [Obsolete], [Serializable], [Conditional], [MethodImpl], [DllImport]), explaining their purpose and how they influence the compiler, runtime, or external tools.
• 5.7. Custom Attributes: Definition, Usage, and Reflection: How attributes are defined, applied to code elements, processed at compile-time by tools, and discovered/interpreted at runtime via reflection.

6. Access Modifiers: Visibility, Encapsulation, and Advanced Scenarios

• 6.1. Fundamental Modifiers (public, private): Their basic scope and usage within a type and within a project.
• 6.2. Assembly-level Modifiers (internal, file C# 11): Controlling visibility across assembly boundaries, including the InternalsVisibleTo attribute for controlled internal exposure.
• 6.3. Inheritance-based Modifiers (protected, private protected C# 7.2, protected internal): Nuances of access within class hierarchies, and the precise distinctions between private protected (accessible only within derived types in the same assembly) and protected internal (accessible within derived types in any assembly, or any type in the same assembly).
• 6.4. Default Access Levels: What default access is applied to types and members if no modifier is explicitly specified.

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Where to Go Next

• Part I: The .NET Platform and Execution Model: Delving into the foundational environment of .NET and how C# code is compiled and executed.
• Part III: Core C# Types: Design and Deep Understanding: Mastering the essential building blocks of C# code, from object-oriented principles with classes and structs to modern type design and nullability.
• Part IV: Advanced C# Features: Generics, Patterns, LINQ, and More: Unlocking C#’s powerful and expressive features, delving into new programming paradigms, dynamic capabilities, and low-level compiler interactions.
• Part V: Concurrency, Performance, and Application Lifecycle: Covering critical aspects of building and maintaining high-performance C# applications, including asynchronous programming, optimization, debugging, and deployment.
• Part VI: Architectural Principles and Design Patterns: Understanding the overarching principles and established design patterns for structuring robust, maintainable, and scalable C# systems.
• Appendix: A collection of resources, practical checklists, and a glossary to support the learning journey.