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Questions and Answers
What is a class in C#?
What does inheritance allow in C#?
What is the purpose of a constructor in a C# class?
Which of the following is NOT a part of a C# class?
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In C#, what does a base class provide to a derived class through inheritance?
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In the given C# code, what does the 'virtual' keyword indicate in the Display method of the Shape class?
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In the given C# code, what happens if the 'x / y' operation in the try block of the Main method throws an exception?
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What happens when an instance of Shape is created and assigned a reference to a Circle object in the given C# code?
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What is the purpose of using the finally block in the exception handling example provided in the C# code?
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What does LINQ (Language Integrated Query) allow developers to do in C#?
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Study Notes
Introduction to C#
C# is a modern, object-oriented programming language developed by Microsoft that runs on the .NET Framework. It is widely used for developing Windows desktop applications, games, web applications, and mobile applications. In this article, we will explore some of the fundamental concepts of C#, including classes, inheritance, polymorphism, exception handling, LINQ, and LINQ to SQL.
Classes
A class in C# is a blueprint for creating objects, which define a new type of object. Classes consist of fields (variables), properties, methods, and constructors. Here is an example of a simple C# class:
using System;
public class Person
{
// Fields
public string name;
public int age;
// Constructor
public Person(string n, int a)
{
name = n;
age = a;
}
// Method
public void Display()
{
Console.WriteLine("Name: {0}", name);
Console.WriteLine("Age: {0}", age);
}
}
In this example, we have a Person class with two fields (name and age), a constructor that initializes these fields, and a Display method that prints the person's name and age.
Inheritance
Inheritance is a fundamental concept in object-oriented programming that allows a new class to be based on an existing class, inheriting all of its properties and methods. In C#, the existing class is called the base class, and the new class is called the derived class. Here is an example of inheritance in C#:
using System;
public class Animal
{
public string name;
public int age;
public void Display()
{
Console.WriteLine("Name: {0}", name);
Console.WriteLine("Age: {0}", age);
}
}
public class Dog : Animal
{
public string breed;
public void DisplayBreed()
{
Console.WriteLine("Breed: {0}", breed);
}
}
public class Program
{
public static void Main()
{
Dog dog = new Dog();
dog.name = "Fido";
dog.age = 3;
dog.breed = "Labrador";
dog.Display();
dog.DisplayBreed();
}
}
In this example, we have a base class Animal with two fields (name and age) and a Display method. We also have a derived class Dog that inherits from Animal and adds a new field (breed) and a new method (DisplayBreed).
Polymorphism
Polymorphism is the ability of an object to take on many forms. In C#, polymorphism is achieved through methods and operators. Here is an example of polymorphism in C#:
using System;
public class Shape
{
public virtual void Display()
{
Console.WriteLine("This is a shape.");
}
}
public class Circle : Shape
{
public int radius;
public override void Display()
{
Console.WriteLine("This is a circle with a radius of {0}.", radius);
}
}
public class Program
{
public static void Main()
{
Shape shape = new Circle();
shape.Display();
}
}
In this example, we have a base class Shape with a Display method. We also have a derived class Circle that overrides the Display method to provide specific information for circles.
Exception Handling
Exception handling is the process of anticipating, detecting, and recovering from exceptional conditions. In C#, exception handling is performed using the try, catch, and finally keywords. Here is an example of exception handling in C#:
using System;
public class Program
{
public static void Main()
{
try
{
int x = 5;
int y = 0;
int z = x / y;
Console.WriteLine("Result: {0}", z);
}
catch (DivideByZeroException ex)
{
Console.WriteLine("Error: {0}", ex.Message);
}
finally
{
Console.WriteLine("Finally block executed.");
}
}
}
In this example, we attempt to divide 5 by 0, which will throw a DivideByZeroException. We use a try block to wrap the potentially exception-throwing code, a catch block to handle the exception, and a finally block to execute cleanup code.
LINQ
LINQ (Language Integrated Query) is a feature of C# that allows developers to write database-style queries in their code. LINQ queries can be used to query any collection that implements the IEnumerable interface, including arrays and lists. Here is an example of a LINQ query in C#:
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
var query = from num in numbers
where num % 2 == 0
select num;
foreach (int num in query)
{
Console.WriteLine(num);
}
}
}
In this example, we have a list of integers and use a LINQ query to filter out the even numbers.
LINQ to SQL
LINQ to SQL is an extension of LINQ that allows developers to query and manipulate data stored in SQL Server databases. Here is an example of LINQ to SQL in C#:
using System;
using System.Data.Linq
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Description
Explore the fundamental concepts of C# programming, including classes, inheritance, polymorphism, exception handling, LINQ, and LINQ to SQL through examples and explanations. Learn about creating objects, overriding methods, handling exceptions, querying collections, and manipulating SQL Server databases.
