最小的 Web API 和播种内存中实体框架数据库

Question

I successfully created a minimal C# ASP.NET Core 6.0 Web API project in Visual Studio 2022 using Microsoft's minimal Web API tutorial located here .

In this tutorial, the author uses an in-memory Entity Framework database. I would like to seed the database with fake data when the program starts.

I'm not sure where or how I can access my DbContext to seed initial data in the database. The author states, "The DI container provides access to the database context and other services." This is correct, but I would like to access the DbContext outside the scope of the Map methods ( app.MapGet , app.MapPost , etc.)

How can I do something like this when the application starts?

db.ToDoEntities.AddRange(new List<ToDoEntity>
{
    new ToDoEntity
    {
        Name = "Code",
        IsComplete = false
    },
    new ToDoEntity
    {
        Name = "Game",
        IsComplete = false
    },
    new ToDoEntity
    {
        Name = "Sleep",
        IsComplete = false
    }
});

db.SaveChanges();

Here is the code I have so far:

// ToDoDbContext.cs
using Microsoft.EntityFrameworkCore;

namespace ToDo.Api;

public class ToDoDbContext : DbContext
{
    public ToDoDbContext(DbContextOptions<ToDoDbContext> options) : base(options) { }
    public DbSet<ToDoEntity> ToDoEntities => Set<ToDoEntity>();
}

// ToDoEntity.cs
namespace ToDo.Api;

public class ToDoEntity
{
    public int Id { get; set; }
    public string Name { get; set; } = "";
    public bool IsComplete { get; set; }
}

// Program.cs
using Microsoft.EntityFrameworkCore;
using ToDo.Api;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
builder.Services.AddDbContext<ToDoDbContext>(options => options.UseInMemoryDatabase("ToDoList"));
builder.Services.AddDatabaseDeveloperPageExceptionFilter();

var app = builder.Build();

// Example GET end-point.
app.MapGet("/to-do-items", async (ToDoDbContext db) => await db.ToDoEntities.ToListAsync());

// All other map operations here. See the tutorial for the full code.

app.Run();

Answer 1

Go to ToDoDbContext and add this method

 protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    //Example
    modelBuilder.Entity<ToDoEntity>().HasData(
    new ToDoEntity{ id= 1, Name = "First", Code = false },
    new ToDoEntity{ id= 2, Name = "First", Code = false ​});
}

then run add-migration through your vs studio terminal
which will generate a migration based on your data seed then run update-database

reference Visit https://docs.microsoft.com/en-us/ef/core/modeling/data-seeding