Connect an Entity Framework application to Neon

This guide describes how to create a Neon project and connect to it from an Entity Framework Core application. The example demonstrates how to set up a basic ASP.NET Core Web API project with Entity Framework Core using Npgsql as the database provider.

To connect to Neon from an Entity Framework application:

1. Create a Neon Project
2. Create a .NET project and add dependencies
3. Configure Entity Framework
4. Run the application

Create a Neon project

If you do not have one already, create a Neon project.

1. Navigate to the Projects page in the Neon Console.
2. Click New Project.
3. Specify your project settings and click Create Project.

Create a .NET project and add dependencies

1. Create a new ASP.NET Core Web API project and change to the newly created directory:

   dotnet new webapi -n NeonEfExample
   cd NeonEfExample

2. Delete the files WeatherForecast.cs and Controllers/WeatherForecastController.cs as we won't be using them:

   rm WeatherForecast.cs Controllers/WeatherForecastController.cs

3. Install required packages

   IMPORTANT

   Ensure you install package versions that match your .NET version. You can verify your .NET version at any time by running dotnet --version.

   dotnet tool install --global dotnet-ef --version YOUR_DOTNET_VERSION
   dotnet add package Microsoft.EntityFrameworkCore.Design --version YOUR_DOTNET_VERSION
   dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL --version YOUR_DOTNET_VERSION

Configure Entity Framework

1. Create a model class in Models/Todo.cs:

   namespace NeonEfExample.Models
   {
       public class Todo
       {
           public int Id { get; set; }
           public string? Title { get; set; }
           public bool IsComplete { get; set; }
       }
   }

2. Create a database context in Data/ApplicationDbContext.cs:

   using Microsoft.EntityFrameworkCore;
   using NeonEfExample.Models;
   
   namespace NeonEfExample.Data
   {
       public class ApplicationDbContext : DbContext
       {
           public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
               : base(options)
           {
           }
   
           public DbSet<Todo> Todos => Set<Todo>();
       }
   }

3. Update appsettings.json / appsettings.Development.json:

   Add the connection string:

   {
     "ConnectionStrings": {
       "TodoDbConnection": "Host=your-neon-host;Database=your-db;Username=your-username;Password=your-password;SSL Mode=Require"
     }
   }

4. Create a Todo controller in Controllers/TodoController.cs:

   using Microsoft.AspNetCore.Mvc;
   using Microsoft.EntityFrameworkCore;
   using NeonEfExample.Data;
   using NeonEfExample.Models;
   
   namespace NeonEfExample.Controllers
   {
       [ApiController]
       [Route("api/[controller]")]
       public class TodoController : ControllerBase
       {
           private readonly ApplicationDbContext _context;
   
           public TodoController(ApplicationDbContext context)
           {
               _context = context;
           }
   
           [HttpGet]
           public async Task<ActionResult<IEnumerable<Todo>>> GetTodos()
           {
               return await _context.Todos.ToListAsync();
           }
   
           [HttpPost]
           public async Task<ActionResult<Todo>> PostTodo(Todo todo)
           {
               _context.Todos.Add(todo);
               await _context.SaveChangesAsync();
               return CreatedAtAction(nameof(GetTodos), new { id = todo.Id }, todo);
           }
       }
   }

5. Update Program.cs:

   using Microsoft.EntityFrameworkCore;
   using NeonEfExample.Data;
   
   var builder = WebApplication.CreateBuilder(args);
   
   builder.Services.AddControllers();
   
   builder.Services.AddDbContext<ApplicationDbContext>(options =>
       options.UseNpgsql(builder.Configuration.GetConnectionString("DefaultConnection")));
   
   builder.Services.AddEndpointsApiExplorer();
   builder.Services.AddSwaggerGen();
   
   var app = builder.Build();
   
   app.UseSwagger();
   app.UseSwaggerUI();
   app.UseAuthorization();
   app.MapControllers();
   
   if (app.Environment.IsDevelopment())
   {
       app.Run("http://localhost:5001");
   }
   else
   {
       app.UseHttpsRedirection();
       app.Run();
   }

6. Create and apply the initial migration:

   dotnet ef migrations add InitialCreate
   dotnet ef database update

Run the application

1. Start the application:

   dotnet run

2. Test the connection by navigating to http://localhost:5001/swagger in your browser. You can use the Swagger UI to create and retrieve Todo items.

Source code

You can find the source code for the application described in this guide on GitHub.

• Get started with Entity Framework and Neon

  Get started with Entity Framework and Neon

Resources

• .NET Documentation
• Entity Framework Core