Added OOP examples

Author: faqeerhussein

.gitignore

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+obj
+bin
+*.sln

classes.cs

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+
+using System;
+
+namespace ClassDemo
+{
+    // This class demonstrates various ways to declare a class,
+    // different property and field implementations, and object creation methods.
+    public class Person
+    {
+        // Private fields
+        // usually their names start with _ (underscore)
+        private string _firstName;
+        private string _lastName;
+        private int _age;
+
+        // Auto-implemented property
+        public string Email { get; set; }
+
+        // Property with a backing field
+        private string _phoneNumber;
+        public string PhoneNumber
+        {
+            get { return _phoneNumber; }
+            set { _phoneNumber = value; }
+        }
+
+        // Read-only property
+        public string FullName
+        {
+            get { return $"{_firstName} {_lastName}"; }
+        }
+
+        // Property with private setter
+        public int Age
+        {
+            get { return _age; }
+            private set { _age = value; }
+        }
+
+        // Static members ( a static property)
+        public static int Population { get; private set; }
+
+        // Default constructor
+        public Person()
+        {
+            _firstName = "Unknown";
+            _lastName = "Unknown";
+            Age = 0;
+            Population++;
+        }
+
+        // Parameterized constructor
+        public Person(string firstName, string lastName, int age)
+        {
+            _firstName = firstName;
+            _lastName = lastName;
+            Age = age;
+            Population++;
+        }
+
+        // Method to demonstrate changing private field through public method
+        public void UpdateName(string firstName, string lastName)
+        {
+            _firstName = firstName;
+            _lastName = lastName;
+        }
+
+        // Method to print Person's detail
+        public string DisplayInfo()
+        {
+            return $"{FullName}, Age: {Age}, Email: {Email}, Phone: {PhoneNumber}";
+        }
+
+        // Static method
+        public static void ShowPopulation()
+        {
+            Console.WriteLine($"Current population: {Population} people created.");
+        }
+    }
+
+    class Program
+    {
+        static void Main()
+        {
+            // Object creation Using default constructor
+            Person person1 = new();
+            Console.WriteLine("Person 1:\n" + person1.DisplayInfo());
+
+            // Object creation Using parameterized constructor
+            Person person2 = new("Faqeer", "Hussain", 41);
+            person2.Email = "[email protected]";
+            person2.PhoneNumber = "03320684191";
+            Console.WriteLine("Person 2:\n" + person2.DisplayInfo());
+
+            // Object creation Using object initializer syntax
+            Person person3 = new()
+            {
+                Email = "[email protected]",
+                PhoneNumber = "0300000000000"
+            };
+            person3.UpdateName("Alice", "Brown");
+            Console.WriteLine("Person 3:\n" + person3.DisplayInfo());
+            
+            // Accessing static method
+            Person.ShowPopulation();
+        }
+    }
+}

classes.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    </PropertyGroup>
+    <ItemGroup>
+        <Compile Include="classes.cs" />
+    </ItemGroup>
+  </Project>

events.cs

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+
+using System;
+
+namespace EventDemo
+{
+    // Step 1: Define a delegate
+    public delegate void SomeEventHandler(object sender, EventArgs e);
+
+    // Publisher class
+    class Publisher
+    {
+        // Step 2: Declare the event
+        public event SomeEventHandler SomeEvent;
+
+        // Method to raise the event
+        public void NotifyAboutEvent(EventArgs e)
+        {
+            // Step 3: Raise/Invoke the event
+            if (SomeEvent != null) // Check if there are any subscribers
+            {
+                SomeEvent(this, e); // Raise/Invoke the event
+            }
+        }
+
+        // Method to simulate an action that triggers the event
+        public void DoSomething()
+        {
+            Console.WriteLine("Publisher is doing something...");
+            // Raise the event when the action occurs
+            NotifyAboutEvent(EventArgs.Empty);
+        }
+    }
+
+    // Subscriber class
+    class Subscriber
+    {
+        // Event handler method
+        public void HandleSomeEvent(object sender, EventArgs e)
+        {
+            Console.WriteLine("Event received by Subscriber.");
+        }
+    }
+
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            Publisher publisherObject = new();
+            Subscriber subscriberObject = new();
+
+            // subscriberObject subscribes to SomeEvent
+            // which is declared in publisherObject's class
+            // by using '+=' operator
+            publisherObject.SomeEvent += subscriberObject.HandleSomeEvent;
+
+            // Trigger the action to raise event in the publisher
+            publisherObject.DoSomething();
+        }
+    }
+}

events.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    </PropertyGroup>
+    <ItemGroup>
+        <Compile Include="events.cs" />
+    </ItemGroup>
+  </Project>

inheritance.cs

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+
+using System;
+
+namespace InheritanceDemo
+{
+    // this is our Base/Parent class
+    public class Person
+    {
+        // Base/Parent class properties
+        public string Name { get; set; }
+        public int Age { get; set; }
+
+        // Base/Parent class method
+        public void DisplayPersonInfo()
+        {
+            Console.WriteLine($"Name: {Name}, Age: {Age}");
+        }
+    }
+
+    // Implementing Inheritance for Student Class
+    public class Student : Person
+    {
+        // Derived/Child class Property
+        public string RollNumber { get; set; }
+
+        // Derived/Child class method
+        public void DisplayStudentInfo()
+        {
+            Console.WriteLine($"Student Roll Number: {RollNumber}");
+        }
+    }
+
+    class Program
+    {
+        static void Main()
+        {
+            // Creating an object of the derived/child class
+            // through Object-initializer technique
+            // accessing properties declared in both
+            // Parent and Child classes
+            Student Asfar = new()
+            {
+                Name = "Asfar Hussain",
+                Age = 12,
+                RollNumber = "IT-2013"
+            };
+
+            // Accessing base/parent class method
+            Asfar.DisplayPersonInfo();
+
+            // Accessing derived/child class method
+            Asfar.DisplayStudentInfo();
+        }
+    }
+}

inheritance.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    </PropertyGroup>
+    <ItemGroup>
+        <Compile Include="inheritance.cs" />
+    </ItemGroup>
+  </Project>