Francesco Ciulla

Posted on Apr 16, 2023 • Updated on May 15, 2023

C# (C Sharp) CRUD Rest API using .NET 7, ASP.NET, Entity Framework, Postgres, Docker and Docker Compose

#dotnet #webdev #beginners #docker

Let's create a CRUD Rest API in C# (or C sharp), using:

.NET 7
ASP.NET (Framework for building web apps)
Entity Framework (ORM)
Postgres (Database)
Docker (Containerization)
Docker Compose (To run the database and the application)

Video version:

All the code is available in the GitHub repository (link in the video description): https://youtube.com/live/PY6uD1fgzZA

🏁 Intro

Here is a schema of the architecture of the application we are going to create:

We will create 5 endpoints for basic CRUD operations:

Create
Read all
Read one
Update
Delete

Here are the steps we are going through:

Define the requirements
Create a new C# project
Install the dependencies
Configure the database connection
Create the logic for the CRUD operations
Update the project
Dockerfile
docker-compose.yml
Run the Postgres database and the application
Update the database schema
Test the application

We will go with a step-by-step guide, so you can follow along.

📋 Requirements:

.NET 7 installed and running
dotnet CLI
(Optional): C# Extension Pack for VS Code ___ ## 🚀 Create a new C# project

There are many ways to create a new C# project, but I will use the dotnet CLI

Open a terminal and run the following command:

dotnet new webapi -n csharp-crud-api

Now step into the directory:

cd csharp-crud-api

📦 Install the dependencies

We will use the following dependencies:

Entity Framework
Npgsql (Postgres driver)

To install them, be sure to be in the csharp-crud-api directory and run the following commands:

dotnet add package Microsoft.EntityFrameworkCore.Design
dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL

🔍 Test the base application

Before we proceed, let's see if the project is configured correctly.

Open the folder in VS Code (or your favorite IDE).

code .

You should see the following structure:

Now run the following command to start the application:

dotnet run --urls=http://localhost:5000

You should see the following output:

To test the application, open a browser and go to the following URL: http://localhost:5000/weatherforecast

You should see the following output:

Now it's time to start coding the application.

📝 Code the application

There are three steps to code the application:

Configure the database connection
Create the logic for the CRUD operations
Update the Program.cs file

🗄️ Configure the database connection

open the appsettings.json file and add the following lines:

{
  "ConnectionStrings": {
    "DefaultConnection": "Host=db;Port=5432;Database=postgres;Username=postgres;Password=postgres"
  }
}

Your appsettings.json file should look like this:

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Host=db;Port=5432;Database=postgres;Username=postgres;Password=postgres"
  }
}

✏️ Create the logic for the CRUD operations

Create a new folder called Models and a new file called User.cs inside it.

Populate User.cs with the following code:

using System.ComponentModel.DataAnnotations.Schema;

namespace Models
{
    [Table("users")]
    public class User
    {
        [Column("id")]
        public int Id { get; set; }

        [Column("name")]
        public string Name { get; set; }

        [Column("email")]
        public string Email { get; set; }
    }
}

Now create a new folder called Data and a new file called UserContext.cs inside it.

Populate the UserContext.cs file with the following code:

using Models;
using Microsoft.EntityFrameworkCore;

namespace Data
{
    public class UserContext : DbContext
    {
        public UserContext(DbContextOptions<UserContext> options) : base(options)
        {
        }

        public DbSet<User> Users { get; set; }
    }
}

Now create a new folder called Controllers and a new file called UsersController.cs inside it.

Populate the UserscController.cs file with the following code:

using Data;
using Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
namespace csharp_crud_api.Controllers;


[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
  private readonly UserContext _context;

  public UsersController(UserContext context)
  {
    _context = context;
  }

  // GET: api/users
  [HttpGet]
  public async Task<ActionResult<IEnumerable<User>>> GetUsers()
  {
    return await _context.Users.ToListAsync();
  }

  // GET: api/users/5
  [HttpGet("{id}")]
  public async Task<ActionResult<User>> GetUser(int id)
  {
    var user = await _context.Users.FindAsync(id);

    if (user == null)
    {
      return NotFound();
    }

    return user;
  }

  // POST: api/users
  [HttpPost]
  public async Task<ActionResult<User>> PostUser(User user)
  {
    _context.Users.Add(user);
    await _context.SaveChangesAsync();

    return CreatedAtAction(nameof(GetUser), new { id = user.Id }, user);
  }

  // PUT: api/users/5
  [HttpPut("{id}")]
  public async Task<IActionResult> PutUser(int id, User user)
  {
    if (id != user.Id)
    {
      return BadRequest();
    }

    _context.Entry(user).State = EntityState.Modified;

    try
    {
      await _context.SaveChangesAsync();
    }
    catch (DbUpdateConcurrencyException)
    {
      if (!UserExists(id))
      {
        return NotFound();
      }
      else
      {
        throw;
      }
    }

    return NoContent();
  }

  // DELETE: api/users/5
  [HttpDelete("{id}")]
  public async Task<IActionResult> DeleteUser(int id)
  {
    var user = await _context.Users.FindAsync(id);
    if (user == null)
    {
      return NotFound();
    }

    _context.Users.Remove(user);
    await _context.SaveChangesAsync();

    return NoContent();
  }

  private bool UserExists(int id)
  {
    return _context.Users.Any(e => e.Id == id);
  }

  // dummy method to test the connection
  [HttpGet("hello")]
  public string Test()
  {
    return "Hello World!";
  }
}

🖋️ Update the `Program.cs` file

We are almost done, now we just need to update the Program.cs file.

add these 2 imports at the top of the file:

using Data;
using Microsoft.EntityFrameworkCore;

And these lines lines above the var app = builder.Build(); line:

// Added configuration for PostgreSQL
var configuration = builder.Configuration;
builder.Services.AddDbContext<UserContext>(options =>
    options.UseNpgsql(configuration.GetConnectionString("DefaultConnection")));

Or you can replace the whole Program.cs file with the following code:

using Data;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// Added configuration for PostgreSQL
var configuration = builder.Configuration;
builder.Services.AddDbContext<UserContext>(options =>
    options.UseNpgsql(configuration.GetConnectionString("DefaultConnection")));

var app = builder.Build();

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

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

We are done with the application logic, now it's time to Dockerize it.

🐳 Dockerize the application

We will Dockerize the application in creating and populating two files:

Dockerfile
docker-compose.yml

🐋 Dockerfile

At the root of the project create a new file called Dockerfile and populate it with the following code:

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
WORKDIR /app

COPY *.csproj ./
RUN dotnet restore

COPY . ./
RUN dotnet publish -c Release -o out

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS runtime
WORKDIR /app
COPY --from=build /app/out ./

ENTRYPOINT ["dotnet", "csharp-crud-api.dll"]

Explanation:

We have 2 stages in the Dockerfile, build and runtime.

Build stage:

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build: This line tells Docker to use the mcr.microsoft.com/dotnet/sdk:7.0 image as the base image for the build stage.
WORKDIR /app: This line tells Docker to set the working directory to /app.
COPY *.csproj ./: This line tells Docker to copy all the .csproj files to the working directory.
RUN dotnet restore: This line tells Docker to run the dotnet restore command.
COPY . ./: This line tells Docker to copy all the files to the working directory.
RUN dotnet publish -c Release -o out: This line tells Docker to run the dotnet publish command.

Runtime stage:
This stage is very similar to the build stage, the only difference is that we are using the mcr.microsoft.com/dotnet/aspnet:7.0 image as the base image.

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS runtime: This line tells Docker to use the mcr.microsoft.com/dotnet/aspnet:7.0 image as the base image for the runtime stage.
WORKDIR /app: This line tells Docker to set the working directory to /app.
COPY --from=build /app/out ./: This line tells Docker to copy the out folder from the build stage to the working directory.
ENTRYPOINT ["dotnet", "csharp-crud-api.dll"]: This line tells Docker to run the dotnet csharp-crud-api.dll command.

🐙 docker-compose.yml

At the root of the project create a new file called docker-compose.yml and populate it with the following code:

version: '3'
services:
  csharp_app:
    container_name: csharp_app
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "8080:80"
    depends_on:
      - db
    environment:
      ConnectionStrings__DefaultConnection: "Host=db;Database=postgres;Username=postgres;Password=postgres"
  db:
    container_name: db
    image: postgres:12
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
      - POSTGRES_DB=postgres
    ports:
      - "5432:5432"
    volumes:
      - pgdata:/var/lib/postgresql/data

volumes:
  pgdata: {}

Explanation:

We define 2 services: csharp_app and db. Csharp_app:
container_name: csharp_app: This line tells Docker to name the container csharp_app.
build:: This line tells Docker to build the image from the Dockerfile.
ports:: This line tells Docker to expose the port 8080 of the container to the port 80 of the host.
depends_on:: This line tells Docker that the csharp_app container depends on the db container.
environment:: This line tells Docker to set the environment variables for ConnectionStrings__DefaultConnection.

Db:

container_name: db: This line tells Docker to name the container db.
image: postgres:12: This line tells Docker to use the postgres:12 image as the base image for the container.
environment:: This line tells Docker to set the environment variables for POSTGRES_USER, POSTGRES_PASSWORD and POSTGRES_DB.
ports:: This line tells Docker to expose the port 5432 of the container to the port 5432 of the host.
volumes:: This line tells Docker to mount the pgdata volume to the /var/lib/postgresql/data directory of the container.

We also need to define the pgdata volume, used by the db container.

We are done. Now we can run the Postgres and the app containers.

🏃‍♂️ Run the application

We will run the containers (services) defined in the docker-compose.yml file.

🐘 Run the Postgres container

docker compose up -d db

📜 Create the table in the database

We can create the table in different ways, but let me show you how you can do it directly from the app container.

First, be sure that the Postgres container is running.

Open a different terminal and run the following command:

docker exec -it db psql -U postgres

And we are inside of the Postgres Container now. We can create the table with the following command:

CREATE TABLE "users" (
  "id" SERIAL PRIMARY KEY,
  "name" VARCHAR(50) NOT NULL,
  "email" VARCHAR(255) NOT NULL
);

🏗️ Build and run the app container

Build the Docker image:

docker compose build

Run the app container:

docker compose up csharp_app

🧪 Test the application

Let's test the application with Postman

Now we can test the project. We will use Postman, but you can use any other tool.

📝 Create a user

To create a new user, make a POST request to localhost:8080/api/users.

The body of the request should be like that:

{
    "name": "aaa",
    "email": "aaa@mail"
}

The output should be something like that:

Let's create two more users, make a POST request to localhost:8080/api/users.

{
    "name": "bbb",
    "email": "bbb@mail"
}

{
    "name": "ccc",
    "email": "ccc@mail"
}

📝 Get all users

To get all users, make a GET request to localhost:8000/api/users.

The output should be something like that:

📝 Get a user

To get a user, make a GET request to localhost:8000/api/users/{id}.

For example GET request to localhost:8000/api/users/1.

The output should be something like that:

📝 Update a user

To update a user, make a PUT request to localhost:8000/api/users/{id}.

For example PUT request to localhost:8000/api/users/2.

The body of the request should be like that:

{
    "name": "Francesco",
    "email": "francesco@mail"
}

The output should be something like that:

📝 Delete a user

To delete a user, make a DELETE request to localhost:8000/api/users/{id}.

For example DELETE request to localhost:8000/api/users/1.

On Postman you should see something like that:

Final test

As a final test, we can check the database using TablePlus.

🏁Conclusion

We made it! we built a CRUD Rest API project in C# (or C sharp), using:

.NET 7
ASP.NET (Framework for building web apps)
Entity Framework (ORM)
Postgres (Database)
Docker (Containerization)
Docker Compose (To run the database and the application)

Video version:

All the code is available in the GitHub repository (link in the video description): https://youtube.com/live/PY6uD1fgzZA

That's all.

If you have any question, drop a comment below.

Francesco

Top comments (22)

VladisS-Vostok2000 • May 15 '23

// POST: api/users
  [HttpPost]
  public async Task<ActionResult<User>> PostUser(User user)
  {
    _context.Users.Add(user);
    await _context.SaveChangesAsync();

    return CreatedAtAction(nameof(GetUser), new { id = user.Id }, user);
  }

Is there expected PostUser?
return CreatedAtAction(nameof(PostUser), new { id = user.Id }, user);

Marc • Apr 17 '23

Check your code formatting. On iOS Chrome at least it’s garbled.

Francesco Ciulla • Apr 17 '23

do you mean the brackts?

Marc • Apr 17 '23

We see:

Let's create two more users, make a POST request to localhost:8080/api/users.

`json
{
"name": "bbb",
"email": "bbb@mail"
}
`

Francesco Ciulla • Apr 17 '23

oh there was a trailing backtick. solved thanks.

SikNik • Aug 5 '23

Thanks for the cool tutorial, also watched your video thanks very much!

Not sure if anyone else picked this up from the walkthrough guide on this page above, at the section where we get users? Its pointing to port 8000 which is invalid and the users only return on port 8080, which is correct in accordance with our configs...

The guide here on this page just says otherwise...

📝 Get all users
To get all users, make a GET request to localhost:8000/api/users.

The output should be something like that:

Francesco Ciulla • Nov 3 '23

oh I will check that, thank you! maybe I was using a different port on that specific part!

Bartek • Apr 20 '23

You could also add validation for User type to prevent incorrect data and reject request on start, not during writing to database. Obviously that will give you ability to check other things such as e.g. format of e-mail addresses.

Francesco Ciulla • Apr 20 '23

that would probably be a good idea

BringABlazer • Apr 19 '23

Very nice - just a question of if it is on purpose that you skipped the explanation of your docker files?

Francesco Ciulla • May 8 '23

fixed, thanks

VladisS-Vostok2000 • May 14 '23

I repeated all steps this awesome guide, but face the problem with creating a user:
MessageText: relation "users" does not exist
I fixed it renaming all colums and table to lower case, and it works.