Ravindra Devrani

How to Backup SQL Server Running in Docker on Linux

Mon, 09 Mar 2026 16:08:51 +0530

I am using mssql server in docker container.
I am using vscode extension named SQL Server (mssql) by microsoft. This extension gives you the feature of creating and exporting the backup
Connect to the database. It should look like this:
Create a backup by using that extension.

Note: I have saved backup inside the folder /var/opt/mssql/data/

To find the exact name:

docker exec <container_name> ls /var/opt/mssql/data/*.bak

Copy backup from docker to host machine:

docker cp <container_name>:/var/opt/mssql/data/your_backup.bak ~/Documents/your_backup.bak

Applying Project Level Vscode Settings with Angular

Wed, 18 Feb 2026 13:47:21 +0530

When you work with a team, everyone has their own preferences like double-quotes vs. single-quotes, trailing semicolon or not. If you want to decide a common code format that automatically applied. There are several ways which also comes with angular 21, like prettier. But you need to run the command for that every time. It is a nice feature. But you can also format code on file save. For that you need to follow these two steps.

Various Learning Techniques

Tue, 17 Feb 2026 18:08:11 +0530

Today we are going explore some popular learning techniques briefly. Yes… this post is not a regular technical blog post of this blog. But it might be helpful you are a “learner” (every programmer is a life long learner). I have described various techniques. Few of them fits very well in learning programming, deepen the concepts and research - while few are best suited for memorizing concepts for exams. Lets learn about each of them.

Dotnet Core Identity With .NET CLI

Tue, 10 Feb 2026 16:05:18 +0530

Aspnet core identity provides an UI to registration, login, manage users, password, external authentication (google, twitter, facebook etc). In simple words, We can say it is an authentication and authorization feature in just few lines of commands and code. It is a nice feature, if you don’t want to use other managed authentication providers like Azure Entra Id / Okta Auth0 etc.

Visual studio provides an UI way to enable identity. Which is very straightforward, but using CLI can be a little bit tricky. It is not always the case you are using visual studio (specially if you are using mac or linux). I use linux also. That is the whole reason to write this article.

Dotnet Core API Crud With Mysql and EF Core

Mon, 29 Dec 2025 11:19:51 +0530

In this tutorial, we are going to make dotnet core web api application and perform all the CRUD (create, read, update and delete). I have tried to keep it simple and avoided any complexities like repository pattern.

💻Source code

Tech and tools used

Dotnet 10
MySql 8+ (in docker container. Click here, if you want to create a MySql container in docker)
Entity Framework Core (ORM)
.NET CLI and VS Code (alternate Visual Studio 2025)

Creating a project

Execute these commands in a sequence.

Dotnet Core API Crud With Mysql and Dapper

Thu, 25 Dec 2025 11:19:51 +0530

💻Source code

Tech and tools used

Dotnet 10
MySql 8+ (in docker container. Click here, if you want to create a MySql container in docker)
Dapper (ORM)
.NET CLI and VS Code (alternate Visual Studio 2025)

Create database

Let’s start with creating a database and a table. You need to execute this script.

How to run Mysql in Docker?

Mon, 22 Dec 2025 18:31:32 +0530

Execute the command below.

For bash:

docker run -d \
 --name mysql-dev \
 -p 3306:3306 \
 -e MYSQL_ROOT_PASSWORD=p@55w0rd \
 -v mysql-data:/var/lib/mysql \
 mysql:8.0.44-debian

For powershell:

docker run -d `
 --name mysql-dev `
 -p 3306:3306 `
 -e MYSQL_ROOT_PASSWORD=p@55w0rd `
 -v mysql-data:/var/lib/mysql `
 mysql:8.0.44-debian

📢 For mac silicon specific:

mysql:8.0.44-debian does not support ARM architectureUse – so use mysql:latest instead of mysql:8.0.44-debian or check official docker hub for suitable image.

LeftJoin and RightJoin in Ef Core 10

Tue, 16 Dec 2025 09:40:05 +0530

Previously there was no simple solution for left or right join. We had to use DefaultIfEmpty or GroupJoin and SelectMany.

With DefaultIfEmpty():

var customerOrders = await (
 from c in ctx.Customers
 join o in ctx.Orders on c.CustomerId equals o.CustomerId into orders
 from o in orders.DefaultIfEmpty()
 select new {
 c.CustomerId,
 c.CustomerName,
 OrderId = o == null ? 0 : o.OrderId
 }
).ToListAsync();

I have used the way described above in most of my career. It was really hard to remember that syntax and I always struggled with that.

It is okay to learn code by mistakes

Tue, 09 Dec 2025 09:00:00 +0530

I am sharing an incident when I was building my first project. I had a cs degree, I knew c# and .net but I’ve never built anything with it except few console and very small windows app. I was writing a code of uploading images and I needed to write the same image upload code in multiple places. It was fine when I’ve copied it in 2 or 3 places, but I was getting annoyed when I had to copy it in multiple places. I did not bother to refactor it. Honestly, I didn’t even know about refactoring. But in future, I had to update the code and I had to update the code in multiple places. Then I got to know about utility or helper methods. Later I learned that it is a concept called DRY (Do not repeat yourself).

Cartesian Explosion and Split Query in Entity Framework Core

Sun, 07 Dec 2025 20:03:37 +0530

In this tutorial, we will understand what cartesian explosion is and how to solve that problem. Let’s look at this query:

var people = await ctx.People
 .Include(p => p.Emails)
 .Include(p => p.Addresses)
 .ToListAsync();

It translates to:

 SELECT "p"."Id", "p"."FirstName", "p"."LastName", "e"."Id", "e"."PersonEmail", "e"."PersonId", "a"."Id", "a"."PersonAddress", "a"."PersonId"
 FROM "People" AS "p"
 LEFT JOIN "Emails" AS "e" ON "p"."Id" = "e"."PersonId"
 LEFT JOIN "Addresses" AS "a" ON "p"."Id" = "a"."PersonId"
 ORDER BY "p"."Id", "e"."Id"

Person joins with Email and Address. Both joins are at the same level.
A person can have multiple emails and adressess.

Let’s say a person with id = 1 have 10 emails and 10 addresses. The query returns 1x10x10 = 100 rows for 1 person. It is just for one person, how much they can be for 100 people. This problem is known as cartesian explosion

How to run Sql Server 2025 in Docker

Thu, 04 Dec 2025 11:00:49 +0530

To be honest, since I have started using docker I have never installed any database in my machine. I use multiple databases and keeping each database up and running takes a toll on resources of your machine. And… you can not install some database like “sql server” on “mac”, then docker is only option for you. Any way, I think it is enough introduction. Let’s get started.

How to run PostgreSql in Docker

Tue, 02 Dec 2025 11:02:49 +0530

Setting Up Node Js With Typescript

Sun, 30 Nov 2025 13:02:07 +0530

(image credit: Gemini)

We are going to create folders and install packages in this step. I don’t have much to say for this tutorial. I have tried to explain necessary stuff through comments. In my opinion code is self-explanatory. So, let’s execute these commands in a sequence.

# create a directory
mkdir backend

# change directory
cd backend

# create the `src` directory inside the `backend`.
mkdir src

# create file
touch src/index.ts 

# initialize node js project. 
# Please stay inside the `backend` directory. 
npm init -y 

# install these packages
npm install express cors

# install the dev dependencies
# these packages won't be shipped to your production bundle
npm install -D typescript tsx @types/node @types/express @types/cors

# generate tsconfig.json file
npx tsc --init

Folder structure should look like this.

Lazy Loading and N+1 Query Problem in Entity framework Core

Thu, 27 Nov 2025 15:34:26 +0530

💻Source code

Lazy loading

You load related entities on demand rather loading at once. This approach is usually useful when you want to load related entities on a certain condition (otherwise always use eager loading).

To enable lazy loading, you need to install this package: Microsoft.EntityFrameworkCore.Proxies

And do following changes in Program.cs

builder.Services.AddDbContext<AppDbContext>(o=>o.UseLazyLoadingProxies()
.UseSqlite("Data Source = mydb.db"));

Look at the example below:

app.MapGet("/", async (AppDbContext context) => {
 foreach (var genre in await context.Genres.ToListAsync()) 
 {
 foreach (var book in genre.Books)
 {
 Console.WriteLine($"===> genre: {genre.Name}, Book: {book.Title}, Price : {book.Author}");
 }
 }
 return Results.Ok("Ok");
});

We are not loading books with genres at once. Rather we are loading books for each genres. Let’s take a look at logs of console.

Content Negotiation in Dotnet Core Webapi

Sat, 22 Nov 2025 16:23:29 +0530

As defined in rfc2616 - “Content nagotiation is the process of selecting the best representation for a given response when there are multiple representations available.”

Clients passes the header Accept with values like application/json,application/xml etc and tells this format is acceptable. Then server gives the response according to that.

In simpler terms, if your API supports xml, json and csv media type, then let clients decide which kind of media type they need as a response.

Containerizing Dotnet App With PostgreSql Using Docker Compose

Fri, 21 Nov 2025 13:33:14 +0530

In this tutorial, we are going to containerize the .NET Web API application with docker and postgres. I am assuming you are familiar with docker. At least, you should have some understandings of how docker works. However, I have covered all the steps needed to create a docker container for your application, but I am not going to cover the theoretical concepts of docker.

📢Last updated : 21-Nov-2025

Containerizing Dotnet App With Sql Server Using Docker Compose

Thu, 20 Nov 2025 13:57:05 +0530

In this tutorial, we are going to containerize the .NET Web API application with docker. I am assuming you are familiar with docker. At least, you should have some understandings of how docker works. However, I have covered all the steps needed to create a docker container for your application, but I am not going to cover the theoretical concepts of docker.

Last updated on:

20-November-2025

🔨Tools needed

Visual Studio Code (Free)
.Net 10.0 SDK (Free)
Docker desktop (Free)

🧑‍💻Tech used

.Net 10.0 Web APIs (controller APIs)
Ms SQL Server 2025 (within a container)
Docker compose

🍵Note: I am using windows 11 operating system. However, I also have tested it in the Linux mint xia and it is working fine.

Fastapi CRUD With Postgres

Sat, 18 Oct 2025 20:18:50 +0530

In this tutorial we learn to create REST Apis with fastapi. We are going to use:

FastApi for creating APIs
PostgreSQL as a database
SQLAlchemy as an ORM tool
Alembic as a migration tool

Tech and tools used

Linux os (you can use window or mac also. But with windows your commands might be a little different. I suggest you to use GitBash in windows)
I am using uv to create project, you can download it from here
Python 3.12
VS Code (code editor) with extension Python by microsoft
PostgreSQL (I am using it in a docker container, you can use installed version too)

The reason I am using uv, because it is pretty fast and I can easily manage dependencies with it.

Azure Key Vault With Dotnet

Mon, 22 Sep 2025 10:25:42 +0530

First of all, let’s see what are we going to achieve? Let’s say we have an dotnet 9 api application.

Its appsettings.json looks like:

 "Color": "Color from appsettings",
 "Person": {
 "Name": "Name from appsettings"
 }

Let’s try to retrieve these values:

app.MapGet("/", (IConfiguration config) =>
{
 string color = config.GetSection("Color").Value ?? "No color";
 string name = config.GetSection("Person:Name").Value ?? "No name";
 return Results.Ok(new
 {
 color,
 name,
 message = "Hello there..."
 });
});

If you visit this endpoint, you will see this output:

Azure App Configuration With Dotnet(C#)

Sat, 20 Sep 2025 16:56:26 +0530

Azure App Configuration is a fully managed service, which provides you a way to store the configurations in a centralized store. You can store configurations of multiple apps in a single place.
It is really helpful for cloud native application (eg. Microservices), which runs on multiple virtual machines and use multiple external services.
It allows us to store Key-value pairs, manage feature flags, and organize configurations using labels and namespaces.
The main benefit is, it supports dynamic refreshing. Which means, you can change config values without restarting the app.
You can also add reference of azure key vault secret here.

Let’s see these things in action.

Azure Blob Storage : CRUD With AspNetCore Mvc & SQL Server

Mon, 08 Sep 2025 12:49:37 +0530

Azure blob storage is a storage solution provided by microsoft. You can store data like images, audio, video, json files, zip files etc etc in the azure.

What are we going to learn?

How to create a web application that stores and manipulate the images in the cloud.
We will perform all the CRUD (create, read, update and delete) operations.

Tech used

.NET Core 9 (MVC app)
SQL server 2022
Azure storage account

High level overview

We will save image url in the database and images in the storage account(blob container)

Let’s create an storage account first

Step 1:

Cosmos DB For NoSQL - CRUD With Dotnet

Sun, 07 Sep 2025 21:37:42 +0530

Azure Cosmos DB for NoSQL is a fully managed and serverless NoSQL and vector database for modern app development, including AI applications and agents. With its SLA-backed speed and availability as well as instant dynamic scalability, it is ideal for real-time NoSQL applications that require high performance and distributed computing over massive volumes of NoSQL and vector data.

Soruce: learn.microsoft.com, you can learn more about it from here

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:

Inversion of Control - Dependency Injection - Dependency Inversion Principle

Sun, 20 Jul 2025 16:10:34 +0530

Direct or traditional approach: Object creates its own dependencies.
Inverted approach (inversion of control): Dependencies are created outside the object. This responsibility is given to someone else.

Example 1 (Direct approach):

We have a service named EmailService which is an implementation of INotificationService.

public interface INotificationService
{
 void SendNotification();
}

public class EmailService : INotificationService
{
 public void SendNotification()
 {
 // code to send notification 
 }
}

OrderService need to use the INotificationService.

Node Js: Jwt Authentication and refresh token

Fri, 04 Jul 2025 00:00:00 +0530

Please visit this post first, where I have made this project from scratch and wrote CRUD APIs.

Source code

Backend and specific only to this tutorial: https://github.com/rd003/ng-node-fullstack/pull/new/jwt-refresh
Complete project with angular : https://github.com/rd003/ng-node-fullstack

JSON web token (JWT) and why it is needed

REST Apis are session less. You can not maintain the authentication session for the whole application. For that purpose, JSON web token (JWT) comes in play. How it works

Build a Node.js REST APIs with Express, Sequelize & SQL Server (2025 Guide)

Thu, 03 Jul 2025 19:17:23 +0530

In this tutorial, you’ll learn how to build a simple CRUD (Create, Read, Update, Delete) REST API using Node.js, Express.js, Sequelize, and SQL Server. I have tried to make it a less verbose. It is more like a technical documentation to create the rest apis in this tech stack. However, I have tried to explain all the essential things. This is ideal if you’re looking to integrate a SQL Server database with a Node.js backend using Sequelize as the ORM. We are using sql server in this tutorial but you can easily replace it with other sql databases.

Dotnet: All you need to know about middlewares

Tue, 27 May 2025 12:49:04 +0530

In dotnet, a Middleware is a piece of code that runs in the request pipeline.
Middlewares are put together in a sequence, and their order matters.
When a request is made, it goes through each of the middleware.
Response flow back in reverse order through the middleware.
Each middleware has capability to modify the request or short circuits the pipeline.
Each middleware can change the response before it’s sent to the client.

Jwt Authention and role base authorization in Dotnet Core

Sun, 18 May 2025 17:11:50 +0530

Create a new web api project

Run these commands in a sequence to create a new project.

dotnet new sln -o JwtDotnet9

cd JwtDotnet9

dotnet sln add JwtDotnet9/JwtDotnet9.csproj

Open the project in vs code.

code .

=> Source Code

=> Securing The .NET 9 App: Signup, Login, JWT, Refresh Tokens, and Role Based Access with PostgreSQL

Install the required nuget packages

dotnet add package Microsoft.AspNetCore.Authentication.JwtBearer

Jwt configuration in appsettings

Open appsettings.json and add these lines

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:

Bulk insert in dapper with table valued parameter

Sun, 04 May 2025 17:00:00 +0530

There might be instances when you want to insert bulk data. For an instance, you want to create an order, where you need to add multiple items. Let’s see how can we insert bulk data in c# using dapper.

Note: It is only good for adding bunch of rows. But if you are looking for adding hundreds of rows then better to use other approaches. There are many, if you look out.

EF Core under the hood: Count() vs Any()

Tue, 01 Apr 2025 11:03:07 +0530

Let’s say you want to execute a code block when Book table is not empty. In Entity Framework Core, we can achieve this in two ways (there might be others but I am unaware of them):

Option 1:

 if(context.Books.Count()>0)
 {
 // do something
 }

Option 2:

 if (context.Books.Any())
 {
 // do something
 }

Note 📢: I am testing these queries against a table containing 1 million rows.

Linux Basic Commands

Thu, 27 Mar 2025 19:52:00 +0530

Contents of a file: ls
Content list with long format: ls -l or ls -l -h human readable or concat the both ls -lh.
Change directory: cd DirectoryName
Move to the upper directory: cd ..
Switch to previous directory : cd -
Change to home directory: cd ~
Go to full path: cd /Home/Documents/Pitctures/MyPictures
Tilde (~) for home directory : MyPc:~/Documents$ cd ~/Videos
Clear screen: clear
Show different drives in the computer (List block devices): lsblk
Opening a file in the text editor :

# open in nano
nano filename

#open in xed editor
xed filename

Root directory: cd /
Press Tab to autocomlete.
Create a directory : mkdir blah
Remove a directory : rmdir blah
Creating a blank file : touch something.txt 14.1. Creating multiple files at once: touch f1.txt f2.txt f3.txt f4.md f5.md
Printing something in terminal : echo hello
Create a file with text: echo "blah blah" > blah.txt
Show contents of a file: cat blah.txt
Copy file : cp /source/filename.ext destination/filename.ext

# note: I am currently in the `Desktop` directory
# copy `blah.txt` from `Desktop` to `Documents` directory

cp blah.txt ~/Documents/blah2.txt

# copy `blah.txt` from `Desktop` to `Documents` directory with changed filename

cp blah.txt ~/Documents/blah2.txt 

# it will copy `blah.txt from `Desktop` to `Documents` directory with changed file name `blah2.txt`

Copy all files (. allfiles.allextensions): cp *.* ~/Documents

How to Install DotNet SDK In Ubuntu Based Distros?

Wed, 26 Mar 2025 19:59:22 +0530

My Distro

I am using linux mint 22.1 which is based on Ubuntu 24.04.

Straightforeward command

sudo apt-get update

sudo apt-get install -y dotnet-sdk-10.0

But…

I have tried to run this command sudo apt-get install -y dotnet-sdk-10.0 but unfortunately I got no success. I have found that, this command works only with Ubuntu 24.10. For Ubuntu 24.04 I need to use different approach.

Uninstall prior version if exists

sudo apt-get remove dotnet-sdk-9.0

Now, run these commands in a sequence:

Dapper: Output Parameter

Sun, 23 Mar 2025 00:00:00 +0530

Stored procedure

CREATE OR ALTER PROCEDURE [dbo].[CreateTrackEntry]
 @EntryDate DATE,
 @SleptAt DATETIME2,
 @WokeUpAt DATETIME2,
 @NapInMinutes SMALLINT,
 @TotalWorkInMinutes SMALLINT,
 @Remarks NVARCHAR(1000) = NULL,
 @TrackEntryId INT OUTPUT
AS
BEGIN
 -- code removed for brevity

END

We have a stored procedure that returns TrackEntryId as an output parameter. Let’s see how can we execute it from the dapper?

using IDbConnection connection = new SqlConnection(_connectionString);

var parameters = new DynamicParameters(trackEntryToCreate);
// Input params
parameters.Add("@EntryDate", trackEntryToCreate.EntryDate);
parameters.Add("@SleptAt", trackEntryToCreate.SleptAt);
parameters.Add("@WokeUpAt", trackEntryToCreate.WokeUpAt);
parameters.Add("@NapInMinutes", trackEntryToCreate.NapInMinutes);
parameters.Add("@TotalWorkInMinutes", trackEntryToCreate.TotalWorkInMinutes);
parameters.Add("@Remarks", trackEntryToCreate.Remarks);

// output params
parameters.Add("@TrackEntryId", dbType: DbType.Int32, direction: ParameterDirection.Output);

await connection.ExecuteAsync("CreateTrackEntry", parameters,commandType:CommandType.StoredProcedure);

int trackEntryId = parameters.Get<int>("@TrackEntryId");

Configuring dotnet core apps for OpenApi with SwaggerUi or Scalar

Fri, 21 Mar 2025 09:16:37 +0530

SwaggerUI, which was previously bundled with .NET Core APIs, has been dropped in .NET 9. However, .NET Core Web APIs still support generating OpenAPI documents. .NET Core apps have built-in support for generating information about endpoints and it uses Microsoft.AspNetCore.OpenApi package for that. To configure interactive UIs for these OpenAPI documents, we have several options. We are going to explore these two:

Swashbuckle SwaggerUI
Scalar

Create a new project, if does not have an existing

Execute these commands in a sequence

Transactions in Dapper

Thu, 20 Mar 2025 09:39:47 +0530

Isn’t it already described in Dapper docs? Sure it is. Why do I bother to write this? Am I just wtiting it for the sake of “posting”? No, I am not. Actually, I was trying to write the code by using Dapper’s docs. Unfortunately, I ran into a few bugs. I am using .NET 9, by the way and this is not even a blog post; it’s just a code snippet. I thought I should share it, may be someone else is facing the same problem as me.

Inserting bulk records (1 million) in SQL Server

Wed, 19 Mar 2025 17:25:31 +0530

Creating a database

USE master
GO

DROP DATABASE IF EXISTS BookMillion
GO

CREATE DATABASE BookMillion
GO

USE [BookMillion]
GO

CREATE TABLE [dbo].[Book](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[Title] [nvarchar](100) NULL,
	[Author] [nvarchar](100) NOT NULL,
	[Country] [nvarchar](100) NULL,
	[ImageLink] [nvarchar](100) NULL,
	[Language] [nvarchar](20) NULL,
	[Link] [nvarchar](200) NULL,
	[Pages] [int] NULL,
	[Year] [int] NULL,
	[Price] [int] NULL

	CONSTRAINT PK_Book_Id PRIMARY KEY (Id)
)
GO

Bulk insert using recursive cte

USE [BookMillion]
GO

WITH Numbers AS (
SELECT 1 AS N
UNION ALL
SELECT N + 1
FROM Numbers
WHERE N < 1000000
)
insert into Book (Title,Author,Country,[Language],ImageLink,Link,Pages,Price,[Year])
select
'Book'+ cast(N as varchar),
'Author'+ cast(N as varchar),
'Country'+ cast(N as varchar),
'Language'+ cast(N as varchar),
'ImageLink'+ cast(N as varchar),
'Link'+ cast(N as varchar),
ABS(CHECKSUM(NEWID())) % 901 + 100, -- Pages between 100-1000
ABS(CHECKSUM(NEWID())) % 901 + 100, -- Price between 100-1000
ABS(CHECKSUM(NEWID())) % 825 + 1200 -- Year between 1200-2024
from Numbers

option (maxrecursion 0)

GO

Keyset Pagination In Entity Framework Core

Sat, 15 Mar 2025 09:50:37 +0530

First we need to know about the traditional offset based pagination and the problems it introduces.

Offset pagination

In the code below we are using the offset pagination.

[HttpGet("offset")]
public async Task<IActionResult> GetBooks(int limit=10, int page=1)
{
 var books = await _context.Books
 .AsNoTracking()
 .OrderBy(a => a.Id)
 .Skip(limit * (page - 1))
 .Take(limit)
 .ToListAsync();
 return Ok(books);
}

Which translates to the following sql:

SELECT
 [b].[Id],
 [b].[Author],
 [b].[Country],
 [b].[ImageLink],
 [b].[Language],
 [b].[Link],
 [b].[Pages],
 [b].[Price],
 [b].[Title],
 [b].[Year]
FROM [Book] AS [b]
ORDER BY [b].[Id]
OFFSET @__p_0 ROWS
FETCH NEXT @__p_1 ROWS ONLY

Note: In every pagination logic, ordering must be unique. In our case we are using Id which is unique.

Rest Api Designing Best Practices

Fri, 07 Mar 2025 10:41:02 +0530

There are some common practices one should take care of while designing REST APIs.

There is also a video version of this post.

1. Use descriptive names for resources

❌ /api/getAllBooks
❌ /api/retrieveBooks
❌ /api/manageBooks
❌ /api/process
✅ /api/books

2. Use nouns not verbs

❌ /api/mangage-books
✅ /api/books

3. Use plural nouns

❌ Singular Nouns	✅ Plural Nouns
/api/book	/api/books
/api/movie	/api/movies
/api/person	/api/people
/api/customer	/api/customers

4. Use hyphens (-) in url for better readabilty

❌ /api/useraccounts
✅ /api/user-accounts

5. Never use crud method names in url

HttpMethod	❌❌❌	✅✅✅
GET	/api/books/GetAllBooks	/api/books
GET	/api/books/GetBookById/{id}	/api/books/{id}
POST	/api/books/CreateBook	/api/books
PUT	/api/books/UpdateBook/{id}	/api/books/{id}
DELETE	/api/books/DeleteBook/{id}	/api/books/{id}

6. Use http method properly

HttpMethod	Endpoint	Description
GET	/api/books	Indicates a get resources
GET	/api/books/{id}	Indicates a get resource with id
POST	/api/books	Indicates creating a resource
PUT	/api/books/{id}	Indicates updating a resource
DELETE	/api/books/{id}	Indicates deleting a resource

7. Use Http StatusCodes Correctly

These are the most commonly used status codes.

Covering Indexes In Sql Server

Sat, 01 Mar 2025 15:20:01 +0530

Table structure and total records

Let’s look at our table structure as shown in the left panel of the picture

Note: There is a non-clustered index on the Title column of the Book table, which has a total of 1 million records.

select
 Id,
 Title,
 Author,
 Price
from Book where title='The Divine Comedy'

As you have noticed in the execution plan, there is a key lookup. Since index is only available for the Title column, Title is retrieved from the non-clustered index. However, other columns like Id, Author and Price are not present in the non-clustered index, so they will be retrieved from the clustered index (the Book table). This results in an additional key lookup step and may decrease the performance. It’s like, you are looking for records in two places (non clustered index and clustered index).

Dotnet Service Lifetime : AddTransient(), AddScoped(), AddSingleton()

Wed, 26 Feb 2025 07:29:14 +0530

Example Setup

I am using a MinimalApi application. Create a new one if you need.

dotnet new webapi -n DITest

Open it in a IDE or editor of your choice.

public interface IMyService
{
 Guid InstanceId { get; }
}

public class MyService : IMyService
{
 public Guid InstanceId { get; }

 public MyService()
 {
 InstanceId = Guid.NewGuid();
 // We are logging in the constructor, so that we get notified whenever the instance is created
 Console.WriteLine($"==> Service created with InstanceId: {InstanceId}");
 }
}

IMyService have a read-only property named InstanceId of type Guid, which is set from the constructor. We are logging inside the constructor, so that we can get notified whenever the new instance is created.

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”.

Database Firsts Approach In EF Core

Mon, 24 Feb 2025 17:49:15 +0530

I have used database first approach in the .NET Framework 4.X. But It is the first time I am trying to use Db First approach in the .NET Core (I am using .net 9). Microsoft refers it ‘Scaffolding (Reverse Engineering)’. Personally I prefer Dapper for DB First approach. May be you have an existing database and you want to use it with ENTITY FRAMEWORK, then this approach might be helpful. I am playing around it and documenting it and sharing that journey with you. Let’s see what it offers.

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:

What Makes My Query Non Sargable?

Mon, 24 Feb 2025 15:51:23 +0530

A query is SARGable (Search ARGument able) if a database engine can take advantage of index.

What makes a query non SARGable?

These are the few factors that makes a query non sargable.

1. Put a column inside a function in the where clause.

select
 s.SalesOrderID,
 s.SalesPersonID,
 s.OrderDate,
 s.SalesOrderNumber
from Sales.SalesOrderHeader s
where YEAR(s.OrderDate) = 2011; -- Row Retrieved: 1607 and Row read : 31465

Note: I have created covering index on the OrderDate:

SQL Server: Table Scan, Clustured Index Scan, Index Seek, RID Lookup, Key Lookup

Mon, 24 Feb 2025 13:40:51 +0530

Initially, it was not intended to be an article. I was tinkering around sql and documenting few things, then I thought, it could turnout to a nice article. I have wrote lots of article and created lots of videos on c#, .net core and angular. But it is my first article on the SQL.

In this blog post, we are going to explore few terms of execution plan, like table scan, clustered index scan, index seek, RID lookup and key lookup.

Creating and Installing Dotnet CLI Tool

Mon, 24 Feb 2025 13:28:51 +0530

In this tutorial we are going to learn:

How to create a cli tool?
How to create a nuget package?
How to install it in our machine.

CLI tools are very useful, they are very easy to use. We are already using it in our every day.

dotnet new console -o CliToolDemo

It is the example of dotnet cli tool, simple way to create a .net console application. You can also create your own cli tools. We are going to use a package created by Microsoft named System.CommandLine , which is a pre-released version as of I am writing this blog post. It is a pre-released version for so long, I wonder what are the plans about this package. You can also use a library named Cocona to create cli tools, which is pretty simple and widely popular. But I am going to stick with System.CommandLine . You should definitely checkout the cocona.

Securing The .NET 9 App: Signup, Login, JWT, Refresh Tokens, and Role Based Access with PostgreSQL

Mon, 24 Feb 2025 11:35:17 +0530

REST APIs are stateless, so server does not store any information about the client. So we can not authorize the rest application in a traditional way. How does a server knows if the user is authenticated user or not? In this situation the Json Web Token (JWT) saves the day.

JSON Web Tokens are an open, industry standard RFC 7519 method for representing claims securely between two parties. Source: jwt.io

Handle Exceptions Globally in .NET Core With IExceptionHandler And IProblemDetailService

Sun, 23 Feb 2025 18:16:31 +0530

Problem details is a standard way to communicate error details in HttpResponse, defined in rfc 7807. Standard ProblemDetails Properties:

Type: URI identifying problem type
Title: Short error description
Status: HTTP status code
Detail: Specific error explanation
Instance: URI identifying specific error occurrence

Problem details is automatically integrated with .net core APIs. When we return the BadRequest we generally get response with problem details.

// controller method
return BadRequest();

// response

{
 "type": "https://tools.ietf.org/html/rfc9110#section-15.5.1",
 "title": "Bad Request",
 "status": 400,
 "traceId": "00-2d4948694b0f223f7f5dff215b42481b-0288bb95d7604783-00"
}

The same thing happens when we return the NotFoundException.

Dotnet Core Api CRUD With Dapper and PostgreSql

Sun, 23 Feb 2025 18:00:17 +0530

💻Source Code: https://github.com/rd003/PostgressDapperDemo

Tools and technology used

VS Code (editor)
.Net 8
Postgres
Dapper

Let’s get started with creating the database first.

create database PersonDb;

Now, create a table within the database.

create table Person
(
 Id serial primary key,
 Name varchar(30) not null,
 Email varchar(30) not null
);

To create a new project you need to run these commands in a sequence.

> dotnet new sln -o PostgressDapperDemo

> cd PostgressDapperDemo

> dotnet sln add .\PostgressDapperDemo\

> code . #this command will open this project in the vs code

Nuget packages

Install the following nuget packages.

Unit of Work With Generic Repository in DotNet Core

Sun, 23 Feb 2025 17:38:31 +0530

The Unit of Work Pattern is all about coordinated changes to the database. It groups multiple operations, such as inserts, updates, and deletes, into one transaction. This simply means that all the changes are done together as a complete action, or they all don’t happen at all. In case something goes wrong in one of the operations, the whole transaction rolls back and keeps the database consistent by not allowing partial updates. This makes it easy to handle errors and ensures reliable data.

Integration Testing in Dotnet With InMemory Db

Sun, 23 Feb 2025 17:04:04 +0530

Integration testing is a software testing technique, where individual units of a program are integrated together and tested as a group for interacting harmoniously with each other. It concerns the testing of interactions and interfaces between modules, components, or systems to see if they behave as expected once integrated.

📢 Always use real database for integration testing instead of InMemory Db.

Purpose

This is to ensure that various components or modules behave according to expectation.
In the case of integration, to find out whether there are problems concerning interfaces or inconsistencies in data.
Verifying whether it meets the set specifications and functionality of an integrated system.

Tech Used in this project

.Net 8 web APIs (controller)
Sqlite
EntityFrameworkCore
xUnit
In Memory Database (for testing)

Let’s get started

Create a sln file (I have named it PersonGithubActionsDemo) with two projects

Unit Testing in Dotnet Core With Nsubstitute

Sun, 23 Feb 2025 16:14:13 +0530

As the name suggesting , Unit testing is a software testing where smallest units of the application such as methods are tested in the isolation, so that we can ensure our software is working as expected.

Commonly used testing frameworks

MSTest
nUnit
xUnit

Mocking frameworks

Mocking framework is a library which allows us to mock the objects. For example, a PeopleController is injected with the IPersonRepository. While testing the PeopleController, we need the IPersonRepository. Mock frameworks comes to rescue in that situation. With the help of mock frameworks we can mock the IPersonRepository and mimic it’s behavior. Some popular mocking libraries are:

Set Bearer Token to Each Request Automatically in Postman

Sun, 23 Feb 2025 13:42:38 +0530

When we work with postman to test the endpoints, and those endpoints are authorized, each time (until it expires) we need to pass the token in the authorization header. To get the token, we need to call the login or authentication API . This process feels quite irritating , because we programmers hates this manual working. We always want an easy and automatic workflow. Let’s see how can we achieve this with postman.

.Net Core API CRUD With PostgreSql

Sun, 23 Feb 2025 13:21:42 +0530

When we create an application with .NET, we tend to use the Microsoft tech stack like Visual Studio IDE, Microsoft SQL Server, Windows Operating System, and Azure. However, things have changed since the introduction of .NET Core. We are no longer bound to a specific operating system and database.

In this blog post, we will learn how to create a Web API CRUD (Create, Read, Update, Delete) application using .NET Core and a Postgres database.

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

Command Pattern With C#

Sun, 23 Feb 2025 11:30:44 +0530

The Command Pattern is a behavioral design pattern that turns a request into a stand-alone object containing all the information about the request. This conversion allows you to parameterize methods with different requests, queue requests, and support undoable operations.

In simpler terms, the Command Pattern encapsulates a request as an object, thereby allowing users to decouple the sender (invoker) from the object that performs the action (receiver).

Adapter Pattern: Bridging the gap between incompatible interfaces

Sun, 23 Feb 2025 11:23:31 +0530

The Adapter pattern is a structural design pattern that allows two incompatible interfaces to work together by converting the interface of one class into an interface expected by the clients. In other words, it acts as a bridge between two incompatible interfaces, enabling them to communicate with each other.

Adapters in real world?

For a phone that does not support a 3.5 mm audio jack, you can use a USB-C to 3.5 mm audio adapter. The phone has only a USB-C port, so the adapter converts the USB-C connection into a 3.5 mm audio jack, allowing you to use traditional wired headphones with your phone. The adapter bridges the gap between the old headphone interface and the new phone design.

Facade Pattern With C#

Sun, 23 Feb 2025 11:07:40 +0530

The Facade pattern is a structural design pattern that provides a simplified interface to a complex system of classes or interfaces.

Let’s understand it with example. Imagine a home automation system.

Let’s implement it programmatically.

public class FacadePatternTestDrive
{
 public static void Main(string[] args)
 {
 ILights lights = new Lights();
 IAirConditioner airConditioner = new AirConditioner();
 ISecuritySystem securitySystem = new SecuritySystem();

 // When leaving home
 lights.TurnOff();
 airConditioner.TurnOff();
 securitySystem.Arm();
 Console.WriteLine("You have left home.");

 // When entering home
 lights.TurnOn();
 airConditioner.TurnOn();
 securitySystem.Disarm();
 Console.WriteLine("Welcome home!");
 }

}

Note: AirConditioner, SecuritySystem and Lights class is not present in the above example for the sake of simplicity. We will write those classes when we implement the facade pattern.

Decorator Pattern With C#

Sun, 23 Feb 2025 10:57:26 +0530

The Decorator pattern is a structural pattern that enables you to wrap an object with additional behaviors or responsibilities without changing its external interface. It’s like adding layers of decorations to a gift — you can add or remove decorations without altering the gift itself.

Example:

Let’s say, we have a book whose base price is 500 INR. Some buyers need a hard cover book which costs some extra money, some need a signed copy which also add some additional cost, some needs the both hard cover and a signed copy which adds more cost. May be in future we want to remove the option of hard cover book or may be we want to add some extra features to it. How do we make our system more flexible, that is the big question.

Observer Pattern

Sun, 23 Feb 2025 10:44:51 +0530

The Observer pattern is a behavioral design pattern that defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.

In a simple words, it is like a publisher and subscriber pattern. When publisher publishes something, all it’s subscriber gets notified.

One Example could be, when we subscribe someone’s mailing list we get notified whenever the publisher publishes something.

Abstract Factory Pattern With C#

Sun, 23 Feb 2025 10:29:26 +0530

The Abstract Factory pattern is a creational design pattern that provides an interface for creating families of related or dependent objects without specifying their concrete classes. It allows a client to create objects from a variety of related classes without needing to know the specifics of their implementations.

GUI Factory Example

Let’s say, we need to create GUI components for different themes in our application. Each theme includes a consistent set of components such as buttons and checkboxes. We want to ensure that the creation of these components is consistent and interchangeable.

Factory Method Pattern with c#

Sun, 23 Feb 2025 10:19:59 +0530

The Factory Method Pattern is a creational design pattern that provides an interface for creating objects in a superclass but allows subclasses to alter the type of objects that will be created.

This pattern is useful when a class cannot anticipate the class of objects it needs to create or when subclasses want to specify the objects to be created.

A Notification System

Imagine we need to develop a notification system that can send different types of notifications such as Email, SMS, and Push Notifications. Each type of notification has a distinct implementation but shares a common interface. Instead of creating each notification type directly in our main logic, we can use the Factory Method Pattern to encapsulate the instantiation process, making our code more modular and extensible.

Understanding Aggregation: How It Differs from Composition

Sun, 23 Feb 2025 08:37:49 +0530

Aggregation is when an object is made up of one or more objects, but those objects can live outside the main object. It defines the has-a relationship.

Note: In the aggregation, if main object is destroyed, its aggregated objects may still live.

Example #1: A Library is an aggregation of Books. Books can live without the library.

Example #2: A Department is an aggregation of Employees. If department closes, the Employees can exist on their own.

Composition: What, Why And When?

Sun, 23 Feb 2025 08:19:49 +0530

Composition is when your class is composed of one or more objects from other classes. A simple example is a Car composed of Engine and Wheel objects. Inheritance defines an “is-a” relationship, while composition defines a “has-a” relationship.

For example, Dog is-a Animal, and Circle is-a Shape. It defines inheritance.

This makes sense because you want to reuse all the features of Animal (eat, sleep, walk, makeNoise) in the Dog class. Cow is-a Animal too, so Cow can also inherit the Animal class. Since cows and dogs make different noises and eat different things, we have to redefine or override the makeNoise() and eat() methods in the Dog and Cow classes. The point is when we want to reuse the functionality of a class and also want subtype polymorphism (Dog and Cow are subtypes of Animal), then we must use inheritance.

The Dependency Inversion Principle (DIP)

Sat, 22 Feb 2025 21:50:00 +0530

The Dependency Inversion Principle states that:

High-level modules should not depend on low-level modules. Both should depend on abstractions (e.g., interfaces).
Abstractions should not depend on details. Details (concrete implementations) should depend on abstractions.

Source: Wikipedia

Other SOLID Principles

Example without DIP

public class UserRepository
{
 public string GetUserById(int id)
 {
 // Code to fetch user from the database
 return "User";
 }
}

public class UserService
{
 private readonly UserRepository _userRepository;

 public UserService()
 {
 _userRepository = new UserRepository();
 }
 public string GetUser(int id)
 {
 return _userRepository.GetUserById(id);
 }
}

One problem with this code is , theUserService is tightly coupled with the UserRepository. Another problem is, if you want to use different implementation of UserReposoitory, you can not easily do it. For instance you want to swap your UserRepsoitory to UserRepositoryWithDifferentDatabase.

The Interface Segregation Principle (ISP)

Sat, 22 Feb 2025 21:35:42 +0530

📢 Clients should not be forced to depend on interfaces they do not use.

In simpler terms, this principle suggests that an interface should not include methods that implementing classes don’t need. It Encourages us to create smaller interfaces over the big fat interface.

Other SOLID principles

Violating example

Imagine you have an interface for workers in a company:

The Liskov Substitution Principle (LSP)

Sat, 22 Feb 2025 20:58:52 +0530

The Liskov Substitution Principle states that a derived type should be completely replaceable for its base type.

In simpler terms, a child class should do at least what the parent class can do. The child class can have additional behaviors, but it must have all the behaviors that the parent class has.

For instance, an Animal has behaviors (eat, sleep, makeSound). A Dog, which is a subtype of Animal, must have all the behaviors (eat, sleep, makeSound).

Open Closed Principle (OCP)

Sat, 22 Feb 2025 19:24:26 +0530

The Open-Closed Principle is one of the five SOLID principles. It states that a class should be open for extension but closed for modification. In other words, you should be able to add new functionality without changing existing code.

Once you have written your class, it should not be modified in the future. However, this doesn’t mean you cannot modify your class during early development stages. It means that once your application or software is in production and you want to introduce the new functionality, you should extend that class rather than modifying it.

Single Responsibility Principle (SRP)

Sat, 22 Feb 2025 19:03:39 +0530

The Single Responsibility Principle (SRP) is a cornerstone of object-oriented design, closely associated with the SOLID principles. It emphasizes that a class should have only one reason to change, meaning it should have a single responsibility or purpose.

What is SRP?

The principle asserts that a class should do only one thing and do it very well. This doesn’t imply that a class should have only one method or behavior, but rather that it should contain a cohesive set of behaviors related to a single responsibility.

Image Upload CRUD Operations in .NET Core WebAPIs

Sat, 22 Feb 2025 18:28:32 +0530

Upload images in .net core apis

In this article, we will learn how to upload/update/delete/read images in .net core APIs. I hate to give long and unnecessary intros, So let’s come to the point’s.

💻 You can get the code from this github repo.

What is the logic behind it? 🤔

When you upload the image (or any file), we will generate the unique image name with it’s extension (eg. uniquename.png). Save the image name in the database and save the file with the same name inside the project. In production apps, you can not simply upload files to the server, you have to give permission to that folder. Or you can use other file storage service, where you will save your files.

Separating the DI Setup From Program.cs file

Sat, 22 Feb 2025 18:18:10 +0530

Let’s take a look at the program.cs file below.

using InventoryMgt.Api.Middlewares;
using InventoryMgt.Data.Repositories;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddTransient<ICategoryRepository, CategoryRepository>();
builder.Services.AddTransient<IProductRepository, ProductRepository>();
builder.Services.AddTransient<IPurchaseRepository, PurchaseRepository>();
builder.Services.AddTransient<IStockRepository, StockRepository>();
builder.Services.AddTransient<ISaleRepository, SaleRepository>();
builder.Services.AddTransient<ExceptionMiddleware>();
builder.Services.AddCors(options =>
{
 options.AddDefaultPolicy(policy =>
 {
 policy.WithOrigins("*").AllowAnyHeader().AllowAnyMethod().WithExposedHeaders("X-Pagination");
 });
});
var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
 app.UseSwagger();
 app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseCors();
app.UseAuthorization();
app.ConfigureExceptionMiddleware();
app.MapControllers();

app.Run();

It is a regular program.cs file. Since we use the dependency injection in our application, we have to register lots of service in our program.cs file. For example:

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.

Generic Delegates (Action, Func & Predicates) in C#

Fri, 21 Feb 2025 09:54:50 +0530

In C#, delegates are used to refer to methods with a specific signature. Generic delegates extend this concept by allowing you to create delegates that can work with any method signature, rather than being tied to a specific signature.

Here’s a basic example of a generic delegate:

delegate T MyGenericDelegate<T>(T arg);

You can use this generic delegate as follows.

MyGenericDelegate<int> handler1 = CustomSquare;
int square=handler1(4);
Console.WriteLine(square); //16

MyGenericDelegate<string\> handler2 = CustomToUpper;
Console.WriteLine(CustomToUpper("helLo")); //HELLO

In-built Generic delegates

C# comes with inbuilt generic delegates like Action, Func and Predicate.

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:

Polymorphism in depth with C#

Thu, 20 Feb 2025 19:49:29 +0530

Polymorphism is one of the core concept of object oriented programming. Word polymorphism = poly (many) + morphism (forms). As its name suggesting polymorphism means, an entity can have multiple forms.

📢 Updated and refinded at : 21-feb-2025

Other oops core concepts :

Let’s learn polymorphism through mistakes.

Jim requires an entry system for his pet shop, which exclusively houses various breeds of dogs. This system will manage the entry and records of all dogs entering and exiting the premises.

Inheritance in C#

Thu, 20 Feb 2025 19:49:18 +0530

📢 Updated and refinded at : 21-feb-2025

Inheritance is a fundamental concept in OOPs that allows a class to inherit properties and behaviors of another class. We have two key terms are here base class/superclass and derived class/subclass.

Base class / super-class: Whose members and functionality are inherited (Giver).
Derived class / sub-class: Who is inheriting the members (Taker)

📺Other oops concepts:

Syntax of inheritance:

Encapsulation in C#

Thu, 20 Feb 2025 19:41:25 +0530

📢 Updated and refinded at : 21-feb-2025

Bundling the data member and member function into a single unit is called encapsulation. Remember the term “capsule”. We put all the medicine inside a wrapper and call it capsule. Similarly, wrap the data members and member functions together is called encapsulation.

Now we need to understand few terms.

Data members : Attributes or properties (eg. name, age)
Member functions: Methods (PrintDetails)

👉 We wrap up the data members (attributes or properties) and member functions (methods) into a single unit (class).

Abstraction in C#

Thu, 20 Feb 2025 19:09:36 +0530

📢 Updated and refinded at : 21-feb-2025

Abstraction allows you to focus on the relevant details of an object while ignoring unnecessary complexities.
This is achieved by defining a simplified representation of an object that hides the implementation details and exposes only the necessary features.
In practical terms, abstraction is implemented through abstract classes and interfaces in languages like C#.

📺Other OOPs related articles :

Fluent Validation in Dotnet Core

Thu, 20 Feb 2025 18:39:45 +0530

Fluent validation

Fluent validation is an open source library for validating the models, which is free as of I am writing this article.

📢 📝 Last Updated: 25-March-2025

Why fluent validation?

If you already have used data annotation for validation, then you must be aware of the validation in .NET. So you might be thinking why do we need a fluent validation then.

Fluent validation helps you to separate validation logic from your models. That makes your code clean. If you have complex validation logic, then you want to define it separately rather than making your model unreadable.

Uploading Images in Blazor Server

Thu, 20 Feb 2025 18:25:51 +0530

In this blog post we are going to learn how to upload files in the blazor server application. I am going to upload images in this tutorial but you can upload any file (i have created reusable code).

💻Source Code: https://github.com/rd003/BlazorFile/

High level overview

We will upload images to a folder of a local machine ( on a production you have to use cloud storage) with a unique name (e.g. sd$3abccc3$1.png ), that name is going to save in database.

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:

Catch Exception Globally in Dotnet Core Apis

Thu, 20 Feb 2025 17:28:02 +0530

There are to ways of catching exception in .net core, one is using try/catch and other one is catching them globally. Although there is nothing wrong with try/catch blog, it is an elegant way of exception handling. Although you can also catch exceptions globally, If you want to log errors in one place. There are various approaches to achieve this, but we will create the custom middleware to achieve it.

Output Caching With Dotnet 7

Thu, 20 Feb 2025 16:20:16 +0530

What is Caching?

Caching is a process of temporarily storing frequently accessed data or resources in a faster and closer location to the user or application, with the goal of reducing the time and resources needed to retrieve that data from its original source. By keeping a copy of the data nearby, caching enables quicker access and improves the overall performance and responsiveness of applications.

JWT Authentication and Role Based Authorization in Dotnet Core

Thu, 20 Feb 2025 10:31:52 +0530

JWT

According to jwt.io JSON Web Tokens are an open, industry standard RFC7519 method for representing claims securely between two parties.

When we create REST APIs, then we don’t want that any one can access those apis. REST APIs, will only be accessed by the authenticated user. We authenticate our user with the help of jwt.

How jwt works?

First, we give an authentication endpoint to user, where he/she puts credential, in return we give a jwt token to user which have an expiry date. To consume any protected resource, user need to pass jwt token on authorization header.

Create Sln File With Multiple Projects

Wed, 19 Feb 2025 22:55:02 +0530

In this article we will learn how to create a .net core project with a Solution (sln file) that contains multiple projects. I know most you guys use visual studio for c# related stuff, but it would be benificial for person who likes to switch with vs code ocassionally, like me or who use linux and forced to use .net cli. Although if you are a new developer and have windows operating system, I will recommend visual studio, because it is the best possible IDE for c# development.

Ngrx Entity and Effects

Wed, 19 Feb 2025 22:29:18 +0530

NGRX Entity gives you an efficient and quick way to deal with ngrx store related operations, such as read, write, update, delete. You can focus on productivity, rather than creating and modifeng complex state everytime. It can be very helpful when you are dealing with complex state and handling with http services at the same time.

What is ngrx ?

Ngrx is a state management library, that stores the state globally. Lets understand some of its components.

Api Versioning in Dotnet Core

Wed, 19 Feb 2025 22:07:03 +0530

Photo by Jan Loyde Cabrera at medium.com

When you are going to do some breaking changes in your apis, it is better to create a new version for that, so that user don’t freaked out. They still can use the older APIs and get ready for new changes. There are various way to create a versions of your APIs like

Query string
URL
HTTP header

If you prefer video version then you can checkout this video with same content.

Angular Autocomlete With Ng Select

Wed, 19 Feb 2025 21:52:46 +0530

There are various packages available for implementing autocomplete in angular and we are going to use the simplest one (ng-select).

Let’s finish talking and need to start write code. Let’s install ng-select package from command line

npm install --save @ng-select/ng-select

Angular pagination with infinite scroll (using ngx-infite-scroll)

Wed, 19 Feb 2025 21:24:41 +0530

Photo by Ajda ATZ on Unsplash

Sometimes we get a condition where you don’t want to display all the data at once. Initially we display some data, and when we scroll down ,we loads more data. This kind of behaviour you can see in youtube, instagram or facebook. You might even spend much time of your day on just scrolling down. So we are gonna learn how to do that.

Write dapper effectively with generic methods

Wed, 19 Feb 2025 17:40:41 +0530

Dapper is a micro ORM for database connectivity in dotnet and it’s been around for quite a while. It is loved by most of the developers because of its simplicity and performance.

Why dapper?

With the help of dapper you can quickly access the data without writing too much code. It performs very well because we directly write queries and executes them. Developers who loves to work with queries and for the projects, where performance really matters where you wants to write very optimized queries, dapper can be the good choice.

Serilog in .NET

Wed, 19 Feb 2025 15:40:41 +0530

In your development journey you have faced so many runtime exceptions. You have handled that with try catch block. But in the runtime you never know where that error has happened and you have to trace that whole section with putting breakpoints. Sometime you have thought that I wish.. I would get notified whenever that exception occur. Then the logging frameworks comes in the play.

About

Mon, 01 Jan 0001 00:00:00 +0000

Ravindra Devrani is fullstack developer, works with .NET and Angular. He has been professionally writing code since 2015. His prefered tech stack is .NET, angular, sql server azure. He also love to explore other tech stack like nodejs, postgres and react. He is more passionate in backend development. In is spare time, he writes blog posts and make technical videos on youtube.

His handles:

Free Courses On My Youtube Channel

Mon, 01 Jan 0001 00:00:00 +0000

Courses

Authentication

Image manipulation

CRUD Apps (Create, Read, Update, Delete)

Project based tutorials on my youtube channel

Mon, 01 Jan 0001 00:00:00 +0000

Either you can checkout the videos or directly use the project, links are available in their description box

1. Ecommerce app for books

This is a basic ecommerse app for selling books. I consider this video as one of my best, in the terms of what it offers. It is 5 hrs 47 min long video, divided in good amount of chapters(timestamps). It offers a lot, except payment gateway. It will be good learning experience for a Beginner. I refined and re-uploaded this video at 5-march-2025. Previously it was built on .NET 7 but now it is upgraded to .NET 9.