Connect an Entity Framework application to Neon

Pre-built prompt for connecting .NET Entity Framework projects to Lakebase Postgres.

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

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.

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

   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

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

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.

• .NET Documentation
• Entity Framework Core

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