C# (pronounced "C-sharp") is a modern, object-oriented programming language developed by Microsoft. It is part of the .NET framework and is used for developing a wide range of applications, from desktop and web applications to mobile and cloud-based applications. C# combines the power of C++ with the simplicity of Visual Basic, making it a versatile and easy-to-learn language.

Basic Syntax and Structure

Comments :
- Single-line comments start with double slashes (//).
- Multi-line comments are enclosed in /* and */.
- XML documentation comments start with triple slashes (///).

Main Method :

The entry point of a C# program is the Main method.

using System;
namespace HelloWorld
{
 class Program
 {
 static void Main(string[] args)
 {
 Console.WriteLine("Hello, World!");
 }
 }
}

Data Types :

Common data types include int, float, double, char, string, and bool.

int age = 25;
float height = 5.9f;
double pi = 3.14159;
char initial = 'A';
string name = "Alice";
bool isActive = true;

Control Structures

Conditional Statements :

if, else if, and else are used for decision making.

if (age > 18)
{
 Console.WriteLine("Adult");
}
else
{
 Console.WriteLine("Minor");
}

Switch Statement :

Used for multi-way branching.

switch (initial)
{
 case 'A':
 Console.WriteLine("Grade A");
 break;
 case 'B':
 Console.WriteLine("Grade B");
 break;
 default:
 Console.WriteLine("Other Grade");
 break;
}

Loops :

for, while, and do-while loops for iteration.

for (int i = 0; i < 5; i++)
{
 Console.WriteLine(i);
}
int j = 0;
while (j < 5)
{
 Console.WriteLine(j);
 j++;
}
int k = 0;
do
{
 Console.WriteLine(k);
 k++;
} while (k < 5);

Functions (Methods)

Defining Methods :

Methods are defined using the return type, method name, and parameters.

static int Add(int a, int b)
{
 return a + b;
}
static void Main(string[] args)
{
 int sum = Add(5, 3);
 Console.WriteLine("Sum: " + sum);
}

Void Methods :

Methods that do not return a value.

static void Greet(string name)
{
 Console.WriteLine("Hello, " + name + "!");
}
static void Main(string[] args)
{
 Greet("Alice");
}

Object-Oriented Programming

Classes and Objects :

Classes define the blueprint for objects.
Objects are instances of classes.

class Dog
{
 public string Name;
 public int Age;
 public Dog(string name, int age)
 {
 Name = name;
 Age = age;
 }
 public void Bark()
 {
 Console.WriteLine(Name + " says woof!");
 }
}
class Program
{
 static void Main(string[] args)
 {
 Dog myDog = new Dog("Buddy", 3);
 myDog.Bark();
 }
}

Inheritance :

Allows a class to inherit attributes and methods from another class.

class Animal
{
 public string Name;
 public virtual void Speak()
 {
 Console.WriteLine("Animal speaks");
 }
}
class Dog : Animal
{
 public override void Speak()
 {
 Console.WriteLine(Name + " says woof!");
 }
}
class Program
{
 static void Main(string[] args)
 {
 Dog myDog = new Dog();
 myDog.Name = "Buddy";
 myDog.Speak();
 }
}

Polymorphism :

Allows methods to do different things based on the object it is acting upon.

class Animal
{
 public virtual void Speak()
 {
 Console.WriteLine("Animal speaks");
 }
}
class Dog : Animal
{
 public override void Speak()
 {
 Console.WriteLine("Dog barks");
 }
}
class Cat : Animal
{
 public override void Speak()
 {
 Console.WriteLine("Cat meows");
 }
}
class Program
{
 static void Main(string[] args)
 {
 Animal myDog = new Dog();
 Animal myCat = new Cat();
 myDog.Speak(); // Output: Dog barks
 myCat.Speak(); // Output: Cat meows
 }
}

Error Handling

Try-Catch Blocks :

Used to handle exceptions and prevent program crashes.

try
{
 int result = 10 / 0;
}
catch (DivideByZeroException e)
{
 Console.WriteLine("Cannot divide by zero!");
}

Finally Block :

Code in the finally block always executes, regardless of whether an exception occurred.

try
{
 int result = 10 / 0;
}
catch (DivideByZeroException e)
{
 Console.WriteLine("Cannot divide by zero!");
}
finally
{
 Console.WriteLine("This will always be printed");
}

Data Access

Connecting to Databases :

C# can interact with databases using ADO.NET.

using System;
using System.Data.SqlClient;
class Program
{
 static void Main(string[] args)
 {
 string connectionString = "Data Source=(local);Initial Catalog=MyDatabase;Integrated Security=True";
 string query = "SELECT * FROM MyTable";
 using (SqlConnection connection = new SqlConnection(connectionString))
 {
 connection.Open();
 SqlCommand command = new SqlCommand(query, connection);
 SqlDataReader reader = command.ExecuteReader();
 while (reader.Read())
 {
 Console.WriteLine(reader["ColumnName"].ToString());
 }
 }
 }
}

Asynchronous Programming

Async and Await :

Asynchronous methods are defined using the async keyword and can use the await keyword to call other asynchronous methods.

using System;
using System.Net.Http;
using System.Threading.Tasks;
class Program
{
 static async Task Main(string[] args)
 {
 string url = "https://jsonplaceholder.typicode.com/todos/1";
 string result = await FetchDataAsync(url);
 Console.WriteLine(result);
 }
 static async Task FetchDataAsync(string url)
 {
 using (HttpClient client = new HttpClient())
 {
 HttpResponseMessage response = await client.GetAsync(url);
 response.EnsureSuccessStatusCode();
 return await response.Content.ReadAsStringAsync();
 }
 }
}

Graphical User Interface (GUI) Development

Windows Forms :

Windows Forms is a GUI class library included as a part of the .NET Framework, providing a platform to create rich desktop applications.

using System;
using System.Windows.Forms;
public class MainForm : Form
{
 private Button button;
 public MainForm()
 {
 button = new Button();
 button.Text = "Click me";
 button.Click += new EventHandler(Button_Click);
 Controls.Add(button);
 }
 private void Button_Click(object sender, EventArgs e)
 {
 MessageBox.Show("Button clicked!");
 }
 [STAThread]
 public static void Main()
 {
 Application.Run(new MainForm());
 }
}

WPF (Windows Presentation Foundation) :

WPF is a UI framework that creates desktop client applications. It uses XAML for front-end design and C# for backend logic.

using System;
using System.Windows;
namespace WpfApp
{
 public partial class MainWindow : Window
 {
 public MainWindow()
 {
 InitializeComponent();
 }
 private void Button_Click(object sender, RoutedEventArgs e)
 {
 MessageBox.Show("Button clicked!");
 }
 }
}

Summary

C# is a powerful and versatile programming language used for developing a wide range of applications. Understanding its basic syntax, control structures, object-oriented principles, error handling, data access techniques, asynchronous programming, and GUI development is essential for building robust and efficient software. C#'s integration with the .NET framework makes it a popular choice for developers working on Windows-based applications.

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