Csharp

In C#, a private constructor is a constructor method declared with the private access modifier (or without mentioning any modifier). If a class have only a private constructor and does not have any public constructor, then you are not able to create the instance of a class. Example 👇

public class Student
{
 Student() { } // private constructor
}

public class Program
{
 static void Main()
 {
 Student stu = new(); //Error CS0122 'Student.Student()'
 // is inaccessible due to its protection level

    }

}

When you try to create the instance of stu, you will the following error.

• Delegates in C# are essentially type-safe function pointers.
• They allow you to treat methods as objects, enabling you to pass methods as parameters, store them in variables, and invoke them dynamically.
• Delegates are particularly useful for implementing callback mechanisms and event handling in C#.

delegate void MyDelegate(string message);

You can point this delegate to any method with similar signature.

namespace BasicsOfCSharp;

// Declare a delegate type
delegate void MyDelegate(string message);

class Program
{
 // Method that matches the delegate signature
 static void DisplayMessage(string message)
 {
 Console.WriteLine("Message: " + message);
 }
 static void Main()
 {
        // Instantiate the delegate.
        MyDelegate handler = DisplayMessage;

        // calling the handler
        handler("Hello..");

    }

}

👉Multicast Delegate:

In c#, Abstract class is a class that can not be instantiated on its own

• In c#, Abstract class is a class that can not be instantiated on its own
• It is typically used as a base class for other class.
• Abstract class provides a way to achieve abstraction, because there you can just declare the methods (abstract methods) and implement them later.
• It can contain both abstract methods (methods without implementation details) and non-abstract methods (method with implementation details).
• Similar goal can be achieved with interface, but in abstract class you can also define non-abstract method. These methods are needed when you need to share some common functionality.

public abstract class Shape
{
 // it is the basic syntax of abstract class
}

Example:

In this tutorial we will se how to read and write data to csv file. It is pretty much easy if you have some external library for that. We are definitely going to use a library and that will be CsvHelper.

You can also check the video version of this tutorial.

First and foremost, create a c# console application in .net core. After that we need to install a nuget package, which is**CsvHelper**

In C#, we can use various approaches to find duplicate elements in array. Each have pros and cons. We will use 3 approaches in this article.

1. Using a HashSet
2. Using a Dictionary
3. Using LINQ

Lets take this array as an example, from this array we will extract distinct numbers and duplicate numbers.

int[] numbers = { 4,7, 2, 3, 4, 5, 3, 6, 7, 8,1, 8 };

We will use this array in all three approaches. So let’s understand one by one.

What is dictionary?

Dictionary is a collection, that store the value in the form of key value pair. It allows you to quick access of value using the key. This data structure is widely used in programming because of its fast look-up time, which makes it ideal for applications that require quick data retrieval

👉 You can not add duplicate key in dictionary

Creating a dictionary: