.NET 7 Web API CRUD Using Entity Framework Core

In this article, we are going to implement a sample .NET 7 Web API CRUD using the Entity Framework Core.

Web API:

Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, and desktop apps.

In simple terminology API(Application Programming Interface) means an interface module that contains programming functions that can be requested via HTTP calls either to fetch or update data for their respective clients.

Some of the Key Characteristics of API:

• Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc.
• Supports default responses like 'XML' and 'JSON'. Also can define custom responses.
• Supports self-hosting or individual hosting, so that all different kinds of apps can consume it.
• Authentication and Authorization are easy to implement.
• The ideal platform to build the REST full services.

Install The SQL Server And SQL Management Studio:

Let's install the SQL server on our local machine. So go to  'microsoft.com/en-in/sql-server/sql-server-downloads' and then download the 'Developer' version and then proceed to install it.

Now install the SSMS(SQL Server Management Studio) IDE at 'https://learn.microsoft.com/en-us/sql/ssms/download-sql-server-management-studio-ssms?view=sql-server-ver16' 

Create A Sample Database:

Let's run the following script to create a sample database.

CREATE DATABASE MyWorldDB

• Here 'MyWorldDB' is the name of our database.

Create A Sample Table:

Let's run the following SQL script to create a new table like 'Students'. While running the below script make sure to select your active database under which we have to create our table.

CREATE TABLE Students (
Id INT IDENTITY(1,1) NOT NULL,
FirstName VARCHAR(200) NULL,
LastName VARCHAR(100) NULL,
Age INT,
Gender VARCHAR(10) NULL
CONSTRAINT PK_Students PRIMARY KEY (Id)
)

• The 'Students' is the name of our table, here we have columns like 'Id', 'FirstName', 'LastName', 'Age', and 'Gender'. The 'Id' column is the primary key column of our table.

Install .NET 7 SDK:

Note: The explicit installation of .NET 7 SDK is only for .NET CLI users. Visual Studio users should have Visual Studio 2022(v17.4) to work with .NET 7 application that will automatically install the .NET 7 SDK.

.NET CLI users must install the .NET 7 SDK, so let go to 'https://dotnet.microsoft.com/en-us/download/dotnet/7.0' and then download the SDK with respect to your local machine.

Create A .NET 7 Web API Application: 

Let's create a .NET 7 Web API sample application to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(Using .NET CLI commands) to create any .NET 7 application. For this demo, I'm using 'Visual Studio Code' editor.

dotnet new webapi -o name_of_your_project

Now run the below command to start our application using .NET CLI.

dotnet watch run --launch-profile https

In our API project 'Program.cs' file is the entry file. So let's explore the default services and middlewares configured in 'Program.cs' file.

Services in 'Program.cs':

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

• (Line:1) The 'AddControllers' service for  API controllers. 
• (Line: 2) The 'AddEndpointAPIExplorer' service gives support for minimal API.
• (Line: 3) The 'AddSwagerGen' service for the swagger page.

Middlewares in 'Program.cs':

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();

• (Lines: 3&4) The Swagger middleware to load the swagger page.
• (Line: 6) The 'UseHttpsRedirection' middleware redirects the 'HTTP' request to 'HTTPs'.
• (Line: 7) The user authorization middleware.
• (Line: 8) The 'MapControllers' is an endpoint middleware that can point the route to the API controller.

SQL ConnectionString:

Let's prepare the SQL connection string.

Sample SQL connection string:

Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=MyWorldDB;Integrated Security=True;Connect Timeout=30

• Data Source - SQL server name.
• Initial Catalog - Database name
• Integrated Security - windows authentication.
• Connect Time - connection time out period.

Entity Framework Core:

Entity Framework Core is an Object/Relational Mapping(ORM) framework. EF Core makes database communication more fluent and easy. The 'DatabaseContext' class acts as a database from our c# code, it will contain all registered classes 'DbSet<TEntity>' (TEntity is any POCO class that represents the table).

Install Entity Framework Core NuGet Packages:

Let's install the Entity Framework Core package

Package manager command
NuGet\Install-Package Microsoft.EntityFrameworkCore -Version 7.0.0

CLI command
dotnet add package Microsoft.EntityFrameworkCore --version 7.0.0

Let's install the Entity Frame Core SQL package

Package manager command
NuGet\Install-Package Microsoft.EntityFrameworkCore.SqlServer -Version 7.0.0

CLI command
dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 7.0.0

Setup Entity Framework Core DatabaseContext:

Now add a new class that represents our 'Students' table. So let's create a new folder like 'Data/Entities' and then add our new class like 'Students.cs'.

Data/Entities/Students.cs:

namespace dot7.API.Crud.Data.Entities;
public class Students
{
    public int Id { get; set; }
    public string? FirstName { get; set; }
    public string? LastName { get; set; }
    public int? Age {get;set;}
    public string? Gender{get;set;}
}

• Here few properties type post-fixed with '?' means those are nullable properties and represent nullable columns in the table.

To manage or control all the table classes in c# we have to create DatabaseContext class. So let's create our context class like 'MyWorldDbContext.cs' in the 'Data' folder.

Data/MyWorldDbContext.cs:

using dot7.API.Crud.Data.Entities;
using Microsoft.EntityFrameworkCore;

namespace dot7.API.Crud.Data;

public class MyWorldDbContext : DbContext
{
    public MyWorldDbContext(DbContextOptions<MyWorldDbContext> context) : base(context)
    {

    }

    public DbSet<Students> Students { get; set; }
}

• (Line: 6)The 'Microsoft.EntityFramework.DbContext' needs to be inherited by our 'MyWorldDbContext' to act as Database context class.
• (Line: 8) The 'Microsoft.EntityFrameworkCore.DbContextOptions' is an instance of options that we are going to register in 'Program.cs' like 'ConnectionString', 'DatabaseProvider', etc.
• (Line: 13) All our table classes must be registered inside of our database context class with 'DbSet<T>' so that the entity framework core can communicate with the table of the database.

In the 'appsettings.Development.json' file add our database connection string.

appsettings.Development.json:

"ConnectionStrings": {
  "MyWorldDbConnection":""
}

Register the Database Context in application DI(dependency injection) services in the 'Program.cs'

Program.cs:

builder.Services.AddDbContext<MyWorldDbContext>(options =>
{
    options.UseSqlServer(builder.Configuration.GetConnectionString("MyWorldDbConnection"));
});

• Here pass the connection string property.

Create A 'Students' API Controller:

In Web APIs controllers are the entry point for the HTTP requests. The 'Action' methods are logical units in the controller which get executed and return the response to the requested clients.

Now create a sample API controller like 'StudentsController' in the 'Controllers' folder.

Controllers/StudentsController.cs:

using dot7.API.Crud.Data;
using Microsoft.AspNetCore.Mvc;

namespace dot7.API.Crud.Controllers;

[ApiController]
[Route("[controller]")]
public class StudentsController: ControllerBase
{
    private readonly MyWorldDbContext _myWorldDbContext;
    public StudentsController(MyWorldDbContext myWorldDbContext)
    {
        _myWorldDbContext = myWorldDbContext;
    }
}

• (Line: 6) Decorated with the 'ApiController' attribute. It provides the API features to the controller, something like API versioning won't work if we don't use the attribute. So it is essential to configure for any controller.
• (Line: 7) Rout attribute defines the URL for API. The default expression '[Controller]' means the URL will contain the controller name(eg: 'Students' will be used in the route). We can define the custom route that can be different from the controller name as well.
• (Line: 8) To make our 'StudentsController' class an API controller it has to inherit the 'Microsoft.AspNetCore.Mvc.ControllerBase'.
• (Line: 10-14) Injected our 'DatabaseContext'(MyWorldDbContext) into our controller constructor.

Read Operation:

Let's create an Action method(which is a logical unit of the controller) for HTTP GET requests. Inside this action method we have to implement logic to fetch all data from the database.

Controllers/StudentsController.cs:

using Microsoft.EntityFrameworkCore;

[HttpGet]
public async Task<IActionResult> GetAsync()
{
	var students = await _myWorldDbContext.Students.ToListAsync();
	return Ok(students);
}

• Here we can observe there is no 'Route[]' attribute on the action method. If our controller contains a single HTTP GET action method then it is optional to add the 'Route[]' attribute. By convention, API will execute the Action methods based on the HTTP verb headers available for every request. But if we have multiple action methods of the HTTP verb types like 'GET', 'POST', 'PUT', and 'Delete' then we have to define the routes per action method explicitly.
• (Line: 3) The 'HttpGet' attribute represents that our action method gets invoked for the HTTP GET requests.
• (Line: 4-8) Defined an asynchronous action method to return the collection of data.
• (Line: 6)  Fetching all records from the 'Students' entity as an async call. The 'ToListAsync' is an extension from the 'Microsoft.EntityFrameworkCor'.
• (Line: 7) The 'Ok()' method creates an OkObjectResult that produces a StatuCodes.Status200Ok(which means 200 success) response.

For to test this endpoint, let's insert some data into our 'Students' table as below.

Now run the application and test our HTTP GET endpoint using the swagger page(which is the developers' page to test the API endpoints)

(Step 1):

(Step2)

Now in our editor terminal, we can observe how the entity framework logs how it creates an SQL query for fetching the data.

Create Operation:

Let's create an Action method(which is a logical unit of the controller) for HTTP POST requests. Inside this action method, we have to implement logic to save a new record into the database.

Controllers/StudentsController.cs:

[HttpGet]
[Route("get-student-by-id")]
public async Task<IActionResult> GetStudentByIdAsync(int id)
{
	var student = await _myWorldDbContext.Students.FindAsync(id);
	return Ok(student);
}

[HttpPost]
public async Task<IActionResult> PostAsync(Students student)
{
	_myWorldDbContext.Students.Add(student);
	await _myWorldDbContext.SaveChangesAsync();
	return Created($"/get-student-by-id?id={student.Id}", student);
}

• (Line: 9) The 'HttpPost' attribute represents our action method that only gets executed for the HTTP POST requests.
• (Line: 10-15) Asynchronous action method for creating the new record into the database.
• (Line: 12) The 'Add' method in a database context begins the tracking for the given new item. This will update the state of the database context as 'EntityState.Added' which means the data is ready to save into the database.
• (Line: 13) The 'SaveChangesAsync()' method saves our data into the database.
• (Line: 14) The 'Created()' method creates a CreatedResult object that produces a status code of 201(created status code) as a response. The 'Created()' method's first parameter will be the URL for endpoint where we can get the newly created item, so to generate  URL we have created another HTTP GET action method as (Line: 1-7) that fetches the data by the 'Id', Here we have added second HTTP GET endpoint so we have added route explicitly. If you want you can use the 'Ok()' method as a return type from the HTTP POST action method as well.

(Step 1)

(Step 2) Let's create a new student record using the HTTP POST endpoint

(Step 3)

Now we can observe how the entity framework core generates the insert query.

(Step 4)

Now access the student by 'id' endpoint to check the newly created item.

(Step 5) Now observe how the entity framework generated the SQL query with where condition by student 'id' value.

Update Operation:

Let's create an Action method(which is a logical unit of the controller) for HTTP PUT requests. Inside this action method, we have to implement logic to update the item data in the database.

Controllers/StudentsController.cs:

[HttpPut]
public async Task<IActionResult> PutAsync(Students studentToUpdate)
{
	_myWorldDbContext.Students.Update(studentToUpdate);
	await _myWorldDbContext.SaveChangesAsync();
	return NoContent();
}

• (Line: 1)The 'HttpPut' represents our action method that gets executed for only HTTP PUT requests. 
• (Line: 2-7) Asynchronous method for updating the records.
• (Line: 4) The 'Update()' method changes the database context state to 'Entity.Modified' which means data is read to update. The 'Update()' method will update all columns for the recorded so make sure this is the case for a full update or not. If you try to pass only a few columns of data then the remaining columns get updated with their default values. One more thing to remember the object should contain 'Id'(primary key) with value.
• (Line: 5) The 'SaveChangesAsync()' method updates the data into the database.
• (Line: 6) The 'NoContent()' method creates a 'NoContentResult' object that produces the empty of status code 204 as a response.

Now test our HTTP PUT endpoint.

(Step 1)

(Step 2)

(Step 3)

(Step 4) Now we can observe how entity framework generates the SQL  update query

Delete Operation:

Let's create an Action method(which is a logical unit of the controller) for HTTP DELETE requests. Inside this action method, we have to implement logic to delete an item from the database.

Controllers/StudentsController.cs:

[Route("{id}")]
[HttpDelete]
public async Task<IActionResult> DeleteAsync(int id)
{
	var studentToDelete = await _myWorldDbContext.Students.FindAsync(id);
	if (studentToDelete == null)
	{
		return NotFound();
	}
	_myWorldDbContext.Students.Remove(studentToDelete);
	await _myWorldDbContext.SaveChangesAsync();
	return NoContent();
}

• (Line: 1) The '[Route]' attribute defined means 'id'(item id value we have to delete) value should be passed as part of URL, and the '{}' expression means any string defined inside of it will be the input parameter to the action method.
• (Line: 2) The 'HttpDelete' attribute represents our action method getting invoked only for the HTTP DELETE requests.
• (Line: 3-13) Asynchronous action method for deleting the record from the database.
• (Line: 5)Fetching the record that needs to be deleted from the database.
• (Line: 6-9)Validating the record to be deleted. If no valid record in the database then we return 'NotFound()' method status code is '404'.
• (Line: 10-11) Removing the record from the database context. The 'SaveChangesAsync()' update the database context to delete the record.
• (Line: 12) The 'NoContent()' status code is '204'.

Let's test our HTTP DELETE endpoint.

(Step 1)

(Step 2)

(Step 3)

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Wrapping Up:

Hopefully, I think this article delivered some useful information on .NET 7 Web API CRUD operations. I love to have your feedback, suggestions, and better techniques in the comment section below.

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