Session 1: In-Depth Explanation

Lecture Topics:

• Introduction to the .NET Framework
• Intermediate Language (IL)
• Assemblies and their structure, EXEs/DLLs
• CLR and its functions
  • JIT Compilation
  • Memory Management
  • Garbage Collection
  • AppDomain Management
  • CLS, CTS
  • Security

No Lab

Lecture: Detailed Explanation

1. Introduction to the .NET Framework

The .NET Framework is a development platform by Microsoft that provides a managed environment for building, deploying, and running applications across various devices and platforms. For PG-DAC February 2025, the focus is on .NET 6, a cross-platform, open-source version of .NET that unifies the .NET ecosystem (replacing .NET Framework, .NET Core, and others).

• Key Features of .NET 6:
  • Cross-Platform: Runs on Windows, macOS, Linux, Android, and iOS.
  • Unified Framework: Combines .NET Framework, .NET Core, Xamarin, and Mono into a single platform.
  • High Performance: Optimized for speed with features like minimal APIs and improved JIT compilation.
  • Support for Modern Development: Includes ASP.NET Core for web apps, Blazor for web UI, and Entity Framework Core for data access.
  • Open Source: Available on GitHub, with community contributions.
  • Long-Term Support (LTS): .NET 6 is an LTS release, supported for three years (until November 2024).
• Components of .NET 6:
  • Common Language Runtime (CLR): Executes managed code, providing services like memory management and security.
  • Base Class Library (BCL): A rich set of reusable classes (e.g., System.String, System.Collections.Generic).
  • Tools: Includes Visual Studio 2022, MSBuild, and the .NET CLI (dotnet command).
  • Languages: Primarily C# (used in this course), but also supports F# and others.
• Why This Matters:
  • Understanding .NET 6 provides the foundation for building modern, cross-platform applications.
  • It’s the backbone for technologies covered in later sessions (e.g., ASP.NET Core, Entity Framework).

2. Intermediate Language (IL)

Intermediate Language (IL), also known as Common Intermediate Language (CIL), is a low-level, platform-agnostic instruction set generated by .NET compilers.

• Definition:
  • When you compile C# code, the compiler (e.g., Roslyn for C#) translates it into IL, stored in assemblies.
  • IL is executed by the CLR’s Just-In-Time (JIT) compiler, which converts it to native machine code at runtime.
• Example:

  • C# code:

    public class Program
    {
        public static void Main()
        {
            Console.WriteLine("Hello, .NET!");
        }
    }
    
    

  • Corresponding IL (viewed with ILDASM):

    .method public hidebysig static void Main() cil managed
    {
        .entrypoint
        ldstr "Hello, .NET!"
        call void [System.Console]System.Console::WriteLine(string)
        ret
    }
    
    

  • Explanation:

    • ldstr: Loads the string "Hello, .NET!".
    • call: Invokes Console.WriteLine.
    • ret: Returns from the method.
• Key Points:
  • IL is platform-independent, enabling .NET’s cross-platform capability.
  • ILDASM (IL Disassembler, covered in Session 2) allows inspecting IL code.
  • IL enables optimizations by the JIT compiler and supports multiple languages (e.g., C#, F#).