Introduction to C# and .NET Framework

Introduction to C# and .NET Framework

• The .NET Framework is a popular integrated software development environment.
• It allows for the integration of code written in different programming languages.
• Previously, each language needed its own execution environment.
• .NET Framework provides a single platform for Windows and web application development.

Generations of .NET Framework

• Various versions exist, including 1.0, 1.1, 2.0, 3.0, 3.5, 4.0 (released 2010), 4.5 (released 2012), 4.6 (released 2015), 4.7 (released 2017), 6.0, and 7.0.

Benefits of .NET Framework

• Provides a consistent programming model, allowing for tasks like database connectivity and file handling.
• Enables language interoperability: code written in one language can be used in another.
• Automatically manages resources (allocation and deallocation of files, memory, and database connections) through garbage collection.

Core Components of .NET Framework

• Common Language Runtime (CLR)
• Common Type System (CTS)
• Common Language Specification (CLS)
• .NET Framework Class Library (FCL)
• Windows Forms
• ASP.NET and ASP.NET AJAX
• ADO.NET
• WPF and WCF

.NET Architecture

• .NET architecture is layered, with Web Services on top, followed by ASP.NET, ADO.NET, Windows Controls, and then Component Model layers, all built on Common Language Runtime.

Common Language Runtime (CLR)

• The core of the .NET platform, providing essential runtime services like automatic memory management and exception handling.
• Acts as an execution engine for various programming languages.
• Loads and runs code written in runtime-aware languages.
• Manages memory, thread execution, and safety, including garbage collection.

MSIL and JIT Compilation

• Source code is compiled into MSIL (Microsoft Intermediate Language), similar to Java bytecode.
• MSIL ensures runtime type safety and security, enabling portable execution across Windows platforms.
• It does not allow pointer tricks or illegal type conversions.

Packaging: Modules, Types, Assemblies, and the Manifest

• A module is a binary (like an EXE or DLL).
• Modules contain type definitions (classes, interfaces, etc.).
• An assembly bundles modules and includes a manifest.
• The manifest catalogs assembly component metadata (name, version, files, type references, scope, and referenced assemblies).

.NET Tools

• Microsoft Visual Studio .NET provides a complete solution for building, deploying, and running XML services for developers.
• Visual Studio .NET is a multi-language development tool designed especially for the .NET platform.
• It enhances existing languages like Visual Basic with new object-oriented features.
• It includes support for C#.

Microsoft C#

• Modern object-oriented programming language built for XML-based web services on the .NET platform.
• Simplicity was a primary design goal over raw power.
• Key features include: simplicity, consistency, type safety, version control, modernity, compatibility, and object orientation.

C# Language

• A type-safe object-oriented language enabling the development of secure and robust applications.
• Syntax is similar to C, C++, and Java.
• Key features include nullable value types, enumerations, delegates, lambda expressions, and direct memory access.

Compile-time and Run-time Relationships of C#

• C# source code is compiled into a managed assembly (e.g., .exe or .dll).
• The managed assembly contains MSIL (Microsoft Intermediate Language), metadata, and references.
• The .NET Framework loads these metadata and references into the CLR.
• The CLR converts the MSIL code to native machine code using the JIT (Just-In-Time) compiler.
• The native machine code is then executed by the operating system.

C# Program Structure

• The structure uses namespaces containing types.
• Types include classes, structs, interfaces, and enums.
• Members include constants, fields, methods, properties, indexers, events, and operators.
• There are no header files. Code is written "inline" with no order dependency on declarations.

Type System

• Value types: hold data directly (cannot be null).
• Examples include primitives, enums, and structs.
• Reference types: hold references to objects in memory; can be null.
• Examples include classes, interfaces, arrays, and delegates.

Predefined Types

• C# predefined types (like int, string, bool etc.) are aliases for system-provided types.
• Example: int is an alias for System.Int32.

Classes

• Single inheritance and multiple interface implementation allowed in C#.
• Class members include constants, fields, methods, properties, indexers, events, and operators.
• Static and instance members for accessing class features.
• Supports nested types and member access (public, protected, internal, and private).

Structs

• Similar to classes but stored in memory directly instead of the heap (e.g., for int, float, double).
• Assignment creates copies of data, not references.
• Ideal for lightweight objects (e.g., Point, Rectangle).
• Benefits include no heap allocation and decreased garbage collection pressure which increases memory efficiency.

Decision Statements

• If-else, ternary, and switch statements are available in C#.

Iteration Statements

• C# supports loops like while, for, foreach, and do..while statements.

The For Statement

• Executes a block of code while a boolean expression is true.

The Foreach Statement

• Executes a block of code for each element in a collection that implements the IEnumerable or IEnumerable<T> interface.

The While Statement

• Executes a block of statements while the specified Boolean expression remains true

The Do Statement

• Executes a block of code at least once, and continues to do so while the specified boolean expression remains true.

C# Special Characters

• @: verbatim identifier character.
• $: interpolated string character.

Raw String Literal Text

• Starts and ends with three double quotes (""").

Verbatim Text

• Indicates a string literal should be interpreted literally.

C# Keywords as Identifiers

• Using @ allows you to use C# keywords as identifiers (e.g. for, if).

String Interpolation

• $: formats strings more readably with string value substitutions.