C Sharp

Sl.No Topic Key Concepts Practical Exercise
1 Setting Up & First Program Installing .NET SDK, Visual Studio Code / Visual Studio, dotnet new console, Console.WriteLine(), Understanding Main() method. Create “Hello World”, personalize it with your name.
2 Variables & Data Types int, double, decimal, bool, char, string, var, declaration, initialization, constants (const). Build a simple program that calculates the area of a circle.
3 Operators & Expressions Arithmetic, assignment, comparison, logical operators. Operator precedence. Create a program to swap two numbers without a third variable.
4 Control Flow: Conditionals if, else if, else, switch expressions (modern C# pattern matching). Build a simple grading system (A, B, C, D, F).
5 Control Flow: Loops for, foreach, while, do-while, break, continue. Print the Fibonacci sequence up to a certain number.
6 Methods & Parameters Defining methods, parameters (value, ref, out), return types, XML comments. Refactor previous exercises into methods.
7 String Manipulation String interpolation ($""), ToString(), String.Format(), common methods (Length, ToUpper(), Substring(), Split()). Build a simple palindrome checker.
8 Arrays & The List<T> int[], string[], looping through collections. Introduction to List<T> and its methods (Add, Remove, Find). Create a program to find the maximum and minimum value in a list of numbers.
9 Debugging Basics Using the debugger in VS Code/VS, breakpoints, stepping through code, watch windows. Debug a pre-written program with intentional bugs.
10 Project 1: Console App Number Guessing Game: The computer generates a random number, and the user has to guess it with hints (“too high”, “too low”). Implement the game using all concepts learned so far.
11 Introduction to OOP: Classes & Objects The class keyword, fields, creating objects with new, constructors. Create a Book class with title and author fields.
12 OOP: Properties & Encapsulation Auto-properties, full properties with get/set accessors, read-only properties, encapsulation principle. Add properties to the Book class and validate data in the setter.
13 OOP: Methods & static Instance methods vs. static methods, the static keyword, Math class example. Add a DisplayInfo() method to the Book class.
14 OOP: Inheritance & Polymorphism The : syntax, base keyword, method overriding (virtual, override), the object base class. Create an EBook class that inherits from Book and adds a FileSize property.
15 OOP: Abstraction & Interfaces abstract classes/methods, interfaces (IEnumerable, IDisposable), defining contracts. Create an ILoanable interface with Borrow() and Return() methods.

16 Exception Handling try, catch, finally, multiple catch blocks, the Exception object, throwing exceptions. Write code that safely parses user input to a number.
17 Advanced Collections Dictionary<TKey, TValue>, HashSet<T>, Queue<T>, Stack<T>, choosing the right collection. Count the frequency of words in a paragraph using a Dictionary.
18 LINQ (Language Integrated Query) Query syntax vs. method syntax, Where, Select, OrderBy, GroupBy, FirstOrDefault. Query a list of objects (e.g., Products) using LINQ.
19 Delegates, Lambdas & Events The Func<> and Action<> delegates, lambda expressions =>, introducing events. Use a delegate to pass a method to filter a list.
20 Project 2: OOP Console App Inventory Management System: Manage a list of products (add, remove, list, search). Use Classes, Lists, LINQ, and File I/O. Build a menu-driven app to manage an inventory.
21 File I/O The System.IO namespace, File.ReadAllText, File.WriteAllText, StreamReader, StreamWriter. Save and load the inventory from Project 2 to a .txt file.
22 Introduction to Databases & SQL (Theory) What is a relational database? Basic SQL: SELECT, INSERT, UPDATE, DELETE. Install SQL Server LocalDB or SQLite and run basic queries.
23 Entity Framework Core I What is an ORM? Installing EF Core NuGet packages, DbContext, DbSet, Code-First approach. Create a BlogContext and Post model class.
24 Entity Framework Core II Configuring connections (appsettings.json), running migrations (Add-Migration, Update-Database). Generate and run a migration to create the database.
25 EF Core: CRUD Operations Creating, Reading, Updating, and Deleting records using your DbContext. Build a simple console app to perform CRUD on your Post model.
26-27 Project 3: Database App Student Registrar: Create a console app to manage students and courses. Use EF Core for all data operations. Model Student and Course classes with a many-to-many relationship.
28 Modern C# Features I record types, init-only properties, pattern matching enhancements (relational patterns). Refactor a Person class to be a record.
29 Modern C# Features II Top-level statements (minimal API), global using directives, file-scoped namespaces. Refactor your first “Hello World” program to use top-level statements.
30 Asynchronous Programming async, await, Task<T> type, HttpClient for API calls, importance in UI and web apps. Write a program to asynchronously fetch data from a public API.

What is .NET Framework?

The .NET Framework is a software development platform developed by Microsoft. It provides a controlled programming environment where software can be developed, installed, and executed on Windows-based operating systems.

It simpifies…

  • Application development.

  • Provide a consistent object-oriented programming environment.

  • Enable code reusability and language interoperability.

  • Support Windows applications, web applications, and web services.

Features of .NET Framework?

Feature Description
Language Interoperability Supports multiple programming languages (C#, VB.NET, F#, etc.) and allows them to work together seamlessly.
Base Class Library (BCL) Provides a rich set of reusable classes, interfaces, and APIs for I/O, data, networking, security, etc.
Common Language Runtime (CLR) The execution engine of .NET; manages memory, security, exception handling, and JIT compilation.
Automatic Memory Management Uses Garbage Collector (GC) to free unused objects and manage memory efficiently.
Security Offers Code Access Security (CAS) and Role-Based Security (RBS) for safe execution.
Simplified Deployment Supports assemblies and versioning to avoid “DLL Hell” issues during deployment.
Cross-language Integration Enables integration of code written in different languages within one project.
Support for Web and Windows Applications Provides frameworks like ASP.NET (web apps), Windows Forms & WPF (desktop apps).
Scalability and Performance Efficient execution through JIT compiler, caching, and optimized runtime features.
Rich Development Tools Works with Visual Studio IDE, offering debugging, GUI designers, and productivity tools.

Comparison table of .NET Framework vs .NET Core

Aspect .NET Framework .NET Core / .NET 5+
Platform Support Windows only Cross-platform (Windows, Linux, macOS)
Deployment Installed system-wide; updates may affect all apps Side-by-side deployment; apps can use different versions
Performance Relatively slower due to legacy architecture High performance with optimized runtime and JIT
Application Types Windows Forms, WPF, ASP.NET Web Forms, ASP.NET MVC ASP.NET Core, Console apps, Cloud-native apps, Web APIs, Blazor
Modern Development Limited support for new tech (Cloud, Containers, Microservices) Built for modern development (Cloud, Docker, Microservices)
Open Source Proprietary (not open source) Open-source, backed by Microsoft and community
Future Support Legacy – no new major updates (only security fixes) Actively developed; future direction of .NET (Unified platform)
Use Cases Enterprise legacy applications, Windows-only desktop apps Modern cross-platform apps, web apps, cloud-native apps, mobile backends
Tooling Visual Studio (Windows only) Visual Studio, Visual Studio Code, JetBrains Rider (cross-platform)
Versioning .NET Framework 4.8 is the last version .NET 5+ is continuously updated and unified

Comparison table c# and Java

Aspect C# Java
Platform Independent Yes Yes
Hardware Independent Yes Yes
Pure OOPs Yes Yes
Open Source Yes (GitHub) Yes
Exception Handling Yes Yes
Multithreadiing Yes Yes
Library -API Namespaces Packages
Intranet Applications / Distributed Apps .Net Remoting RMI
Collection API System.Collection java.util
Versioning .NET Framework 4.8 is the last version .NET 5+ is continuously updated and unified
CUI Yes Yes
GUI Windows, WPF AWT, Swings, JFX
Database ADO.Net JDBC
Web Applications ASP.Net, ASP.Net Core Servlets, JSP
Client Side scripting Blazor JavaScript
Mobile Applications C# with Xamarin Android with Java
ORM Implementation EF, EF.Net JPA – Hibernate
Machine Learning ML.Net –
Cloud Applications Azure Quarkus, Micronaut, Spring, Spring boot
What Main( ) in C# ?

The Main method is the entry point of a C# application. It is the first method that is executed when you run your program. The operating system calls this method to start your application.

Signature (The Common Forms)

// Takes no arguments, returns nothing.
static void Main()
{
     // Your code here
}
// Takes command-line arguments as an array of strings, returns nothing.
// This is the most commonly used form.
static void Main(string[] args)
{
     // Your code here. 'args' contains parameters passed from the command line.
     // Example: > myapp.exe hello world
     // Then: args[0] is "hello", args[1] is "world"
}
// Can also return an integer (typically used for error codes).
// 0 usually means success; non-zero means an error.
static int Main(string[] args)
{
    // Your code here
    return 0; // Success
}

Key Characteristics

  • static: It belongs to the class itself, not to a specific object instance. This allows the runtime to call it without creating an object first.

  • Naming: It must always be capitalized as Main (not main like in Java/C++).

  • Accessibility: It is typically private (the default if no access modifier is specified) but can be public. The runtime can call it either way.

Identifiers in C#

Identifiers are the names given to various programming elements in C# such as variables, methods, classes, namespaces, arrays, etc. They help the compiler and the programmer uniquely identify each item in a program.

Rules for Identifiers in C#:

Identifiers are the names given to various programming elements in C# such as variables, methods, classes, namespaces, arrays, etc. They help the compiler and the programmer uniquely identify each item in a program.

  • Must begin with a letter, underscore (_), or @ symbol.

    • Cannot start with a digit.

  • Can contain letters, digits, and underscores (_).

    • No special characters (like %, $, #) allowed.

  • Case-sensitive.

    • Example: age and Age are two different identifiers.

  • Cannot be a C# keyword.

    • Example: int, class, static cannot be used as identifiers.

  • No spaces allowed.

    • Use camelCase or PascalCase instead.

  • Length can be large, but should be meaningful.

Valid and Invalid Examples:

Valid Identifiers Invalid Identifiers
studentName 123name (starts with digit)
_totalMarks total-marks (hyphen not allowed)
Age float (keyword)
employee_salary emp salary (spaces not allowed)
@class (keyword with @ prefix) #score (special character)

Special Case: @ Identifiers:

C# allows using keywords as identifiers if prefixed with @. For example,

int @int = 5; // valid, even though “int” is a keyword
Console.WriteLine(@int);

Best Practices for Identifiers:

  • Use meaningful names (e.g., studentAge instead of x).

  • Follow naming conventions:

    • camelCase for variables & methods → studentName

    • PascalCase for classes & methods → StudentDetails

    • ALL_CAPS for constants → PI_VALUE

Keywords in C#

Keywords are reserved words in C#. They have predefined meanings in the language and cannot be used as identifiers (variable names, class names, etc.).

C# Keywords List:

Category Keywords
Data Types bool, byte, sbyte, char, decimal, double, float, int, uint, long, ulong, short, ushort, object, string, void
Control Flow if, else, switch, case, default, while, do, for, foreach, in, break, continue, goto, return, yield
Modifiers public, private, protected, internal, static, readonly, sealed, const, volatile, abstract, virtual, override, unsafe, extern, partial, new
Class & Object Related class, struct, interface, enum, namespace, delegate, event
Inheritance & Polymorphism base, this, new, override, abstract, sealed
Exception Handling try, catch, finally, throw
Access & Reference ref, out, in, params, typeof, sizeof, stackalloc, fixed
Operators & Expressions is, as, typeof, checked, unchecked
Contextual Keywords (used in special contexts) var, dynamic, async, await, nameof
Others true, false, null, using, lock

Data Types in C#

A data type in C# defines:

  • The type of data a variable can store (integer, floating-point, text, etc.).

  • The size in memory and the range of values it can hold.

  • The operations that can be performed on the data.

Categories of Data Types in C#:

C# data types are broadly divided into three categories:

  1. Value Types
  2. Reference Types
  3. Pointer Types

Value Types:

  • Store data directly in memory.

  • Examples: numbers, characters, boolean.

  • Stored in stack memory.

  • Includes:

    • Integral types: int, short, long, byte, sbyte, ushort, uint, ulong

    • Floating-point types: float, double, decimal

    • Other types: char, bool, enum, struct

Reference Types:

  • Store a reference (address) to the data, not the actual data.

  • Stored in heap memory.

  • Includes:

    • string

    • object (base type of all data types)

    • class, interface, delegate, array

Pointer Types:

  • Store the memory address of another variable.

  • Used in unsafe code only.

Data Types in C# with Sizes and Ranges:

Data Type Size Range
byte 8-bit 0 to 255
sbyte 8-bit -128 to 127
short 16-bit -32,768 to 32,767
ushort 16-bit 0 to 65,535
int 32-bit -2,147,483,648 to 2,147,483,647
uint 32-bit 0 to 4,294,967,295
long 64-bit -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
ulong 64-bit 0 to 18,446,744,073,709,551,615
float 32-bit ~±1.5e−45 to ±3.4e38 (7 digits precision)
double 64-bit ~±5.0e−324 to ±1.7e308 (15-16 digits precision)
decimal 128-bit ±1.0e−28 to ±7.9e28 (28-29 digits precision)
char 16-bit (Unicode) Single character (e.g., ‘A’)
bool 1-bit (stored as 1 byte) true or false
string (Reference type) Sequence of characters
object (Reference type) Base type of all data types

An operator in C# is a symbol that tells the compiler to perform a specific operation on one or more operands (variables, constants, values).

Types of Operators

C# provides several categories of operators:

  1. Arithmetic Operators
  2. Relational (Comparison) Operators
  3. Conditional (Ternary) Operator
  4. Logical Operators
  5. Assignment Operators
  6. Unary Operators
  7. Bitwise Operators
  8. Type Operators

Arithmetic Operators:

Used for basic mathematical operations

OperatorDescriptionExample
+Additiona + b
-Subtractiona - b
*Multiplicationa * b
/Divisiona / b
%Modulus (remainder)a % b

Relational (Comparison) Operators

Used to compare values; result is true or false.

OperatorDescriptionExample
==Equal toa == b
!=Not equal toa != b
>Greater thana > b
<Less thana < b
>=Greater than or equal toa >= b
<=Less than or equal toa <= b

Conditional (Ternary) Operator

It is shorthand for if-else condition.

Syntax:

     condition ? expression1 : expression2;

Logical Operators

Used with boolean values.

OperatorDescriptionExample
&&Logical AND(10 > 5 && 7 < 10)
||Logical OR(10 > 5 || 7 > 10)
!Logical NOT!(a > b)

Assignment Operators

Used to assign values to variables.

OperatorDescriptionExample
=Assigna = 10
+=Add and assigna += 5 (same as a = a + 5)
-=Subtract and assigna -= 5
*=Multiply and assigna *= 5
/=Divide and assigna /= 5
%=Modulus and assigna %= 5

Unary Operators

Work on a single operand.

OperatorDescriptionExample
+Unary plus (no change)+a
-Unary minus (negation)-a
++Increment (prefix or postfix)a++, ++a
--Decrement (prefix or postfix)a--, --a
!Logical NOT!true → false

Bitwise Operators

Operate on bits.

OperatorDescriptionExample
&Bitwise ANDa & b
``Bitwise OR
^Bitwise XORa ^ b
~Bitwise NOT (complement)~a
<<Left shifta << 2
>>Right shifta >> 2

Type Operators

Used for type checking and casting.

OperatorDescriptionExample
isChecks if object is a certain typeif (x is int)
asSafe type castingobj as string
typeofReturns type of classtypeof(int)
sizeofReturns size of data typesizeof(int)
checkedChecks overflow at runtimechecked { int x = int.MaxValue + 1; }
uncheckedIgnores overflowunchecked { int x = int.MaxValue + 1; }
What is Value type

Value Types store their data directly in memory where the variable is allocated. When you assign one value type to another, a copy of the value is created.