Csharp on Ravindra Devrani

Asynchronous Programming in C# - Comparing it with multi-threading

Tue, 29 Jul 2025 18:24:07 +0530

Asynchronous task is a non-blocking task. Main thread goes back to the thread pool (and free to do other tasks) when it reaches to await – and new thread is assigned when wait is complete.

It is different from the multi-threading. In multi-threding, task is divided between multiple threads. Cores of your CPU are utilized.

Analogy

Let’s say you have some chores like:

Boiling eggs 🫕 (or sweet potatoes🍠🍠 if you dont eat eggs 🥚🥚)
Clean 🧹🪣 the house

There are multiple ways to achieve this:

C#: Byte and Its Use Cases

Sat, 17 May 2025 17:32:06 +0530

byte is a value type in c#
byte is an unsigned integer which stores value from 0 to 255, which means it can not store negetive numbers.
Size of byte is 8-bit (1 byte)
CTS equivalent of byte is System.Byte
It’s default value is 0
It is great for memory optimization when dealing with small numbers.

Examples:

byte a = 10;

Console.WriteLine(a);

Use cases

Working with ASCII value

 byte asciiValue = (byte)'R'; // 82
 byte asciiValue2 = (byte)'r'; // 114

Encoding text into bytes

 using System.Text;

 string message = "Ravindra";
 byte[] encoded = Encoding.UTF8.GetBytes(message);

 Console.WriteLine($"{string.Join(",",encoded)}");

 // op: 82,97,118,105,110,100,114,97

Note: Each character is encoded using UTF-8. For standard letters, the byte values match their ASCII codes.. (R: 82, a:97, v:118 …)

IEnumerable Vs IQueryable In C#

Tue, 13 May 2025 11:45:17 +0530

There has been a discussion around town about the difference between an IEnumerable and an IQueryable, especially in c# interviews. I won’t be diving into the fact that IEnumerable is part of the System.Collections namespace and IQueryable belongs to System.Linq namespace (or did I???). Rather, I’ll focus on the practical usage of both—how they work, and when to use each.

IQueryable

 public IActionResult GetPeople()
 {
 // It will retrieve 2 records from database 
 IQueryable<Person> people = _context.People.Take(2); 
 // Note: At the above line, no data will be retrieved from the database

 return Ok(people); // Data will be retrieved here
 }

Corresponding sql

Note that, I am using Sqlite, the above code is translated to this query:

LINQ: Zip() operator

Tue, 25 Feb 2025 10:10:41 +0530

There is also a video version of this tutorial.

Let’s understand it with example.

int[] nums1 = [1, 2, 3, 4];
int[] nums2 = [3, 4, 5, 6];

IEnumerable<int>? product = nums1.Zip(nums2, (n1, n2) => n1 * n2);

Console.WriteLine(string.Join(", ", product)); // 3, 8, 15, 24

Let’s break it down:

IEnumerable<int>? product = nums1.Zip(nums2, (n1, n2) => n1 * n2);

It takes nums1[i] and nums2[i], evaluates it (nums1[0]*nums2[0]) and returns it. Here i is the index of the array. For example.

SingleAsync vs SingleOrDefaultAync vs FirstAsync vs FirstOrDefaultAsync vs FindAync

Mon, 24 Feb 2025 18:07:04 +0530

I don’t think there is any need of introduction. Let’s jump to the code section. We coders understand with code more. Let’s understand the concept then you don’t need to remember any definition.

This is the recordset against which I am running queries.

Id	FirstName	LastName
1	John	Doe
2	Ravindra	Devrani
3	Mohan	Singh
20	Mahesh	Soni
21	John	Snow

First and foremost let’s say we need a record with LastName=”Doe”.

Curious Case of LINQ Group By

Mon, 24 Feb 2025 16:17:33 +0530

Schema

Department (DepartmentId, Name)
Employee (EmployeeId, Name, DepartmentId)

Result set I need

Show all departments with total number of employees. Do not skip the departments which have 0 employees. As shown below:

DepartmentIdNameTotalEmployees1Engineering22Marketing13HR0

I have applied various queries and checked their equivalent sql.

1. Straightforward but skips the department which has no employees

This query does not meet my requirement. It would be a good choice if I don’t need departments without any employees.

LINQ: SelectMany()

Mon, 24 Feb 2025 16:09:29 +0530

NOTE: You can find the source code here.

Schema Overview

// Department
public class Department
{
 public int DepartmentId { get; set; }
 public string Name { get; set; } = string.Empty;

 public ICollection<Employee> Employees { get; set; } = [];
}

// Employee

public class Employee
{
 public int EmployeeId { get; set; }
 public string Name { get; set; } = string.Empty;

 public int DepartmentId { get; set; }

 public Department Department { get; set; } = null!;

 public ICollection<EmployeeSkill> EmployeeSkills { get; set; } = [];
}

// Skills

public class Skill
{
 public int SkillId { get; set; }
 public string Name { get; set; } = string.Empty;

 public ICollection<EmployeeSkill> EmployeeSkills { get; set; } = [];
}

// EmployeeSkills (Junction table)

public class EmployeeSkill
{
 public int EmployeeId { get; set; }
 public int SkillId { get; set; }

 public Employee Employee { get; set; } = null!;
 public Skill Skill { get; set; } = null!;
}

In simpler terms:

Higher Order Functions in C#

Sun, 23 Feb 2025 13:07:13 +0530

Higher-order functions (HOF) are functions that can take a function as an argument or return a function or both. In C#, higher-order functions are achieved using delegates, lambda expressions and expression trees.

Example 1: Using a Delegate

// Declare a delegate that takes an int and returns an int
public delegate int IntOperation(int x);

public class Program
{
 // Higher-order function that takes a delegate as an argument
 public static int PerformOperation(int value, IntOperation operation)
 {
 return operation(value);
 }

 public static void Main()
 {
 // Create a delegate instance that points to the Square method
 IntOperation square = x => x \* x;

 // Pass the delegate to the higher-order function
 int result = PerformOperation(5, square);
 Console.WriteLine(result); // Output: 25
 }

}

Example 2 : Using lambda expression

// Higher-order function that takes a lambda expression as an argument
public static int PerformOperation(int value, Func<int, int\> operation)
{
 return operation(value);
}

// main method

// Define a lambda expression that squares a number
Func<int, int> square = x => x * x;

// Pass the lambda expression to the higher-order function
int result = PerformOperation(5, square);

Example 3: Function as a Return Value

public class Program
{
 // Higher-order function that returns a function
 public static Func<int, int\> GetOperation(bool isSquare)
 {
 if (isSquare)
 {
 return x => x \* x;
 }
 else
 {
 return x => x + x;
 }
 }

 public static void Main()
 {
 // Get a function that squares a number
 Func<int, int> operation = GetOperation(true);

 // Use the returned function
 int result = operation(5);
 Console.WriteLine(result); // Output: 25
 }
}

In c#, higher order functions are everywhere. If one have used LINQ, must have used HO functions. Collection’s Where() is the good example.

Let's dive into various types of properties in c#

Sun, 23 Feb 2025 12:48:39 +0530

I assume you have some knowledge of C# properties. If not, here’s a quick definition: A property is a class member that provides a flexible way to read, write, or compute the value of a private field. Don’t worry if you’re new to properties; we’ll be using them in this blog, and I’ll explain them as we go along.

1. Properties with getter and setter

public class Person
{
 public string Name { get;set; }
 public int Age { get; set;}
}

Generally, we define properties like this. The Person class has two properties Name and Age, each with getters and setters. This enables you to set and read their values.

Understanding The Pure And Impure Functions in C#

Sun, 23 Feb 2025 11:38:07 +0530

Pure functions

Pure function is that:

Always returns the same output given the same inputs.
Does not modify the state of object or any external state.
Does not have any side effects such as I/O operations, exceptions or modifying external variables.

In other words, a pure function takes input, process it and returns the output without modifying anything else.
Pure functions are easy to test and debug.

Examples

Mathematical calculations

public int Add(int a, int b)
{
 return a + b;
}

String manipulation

public string Concatenate(string a, string b)
{
 return a + b;
}

Array operations

public int[] SortArray(int[] array)
{
 return array.OrderBy(x => x).ToArray();
}

Data transformations

public string ConvertToString(int value)
{
 return value.ToString();
}

Validation

public bool IsValidEmail(string email)
{
 return email.Contains("@");
}

Impure Functions

Impure function is that

Private Constructor in C#

Fri, 21 Feb 2025 10:20:08 +0530

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, Anonymous Method and Lambda Expression

Fri, 21 Feb 2025 09:31:26 +0530

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:

Abstract Class in C#

Fri, 21 Feb 2025 09:20:13 +0530

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:

Easiest Way to Handle Csv Files in Csharp

Thu, 20 Feb 2025 17:58:49 +0530

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**

Multiple Ways to Find Duplicates in Csharp Array

Thu, 20 Feb 2025 17:49:19 +0530

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.

Using a HashSet
Using a Dictionary
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.

C# Dictionary and Its Use Cases

Thu, 20 Feb 2025 17:40:42 +0530

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: