如何在OnSignedIn .net核心实体框架中访问数据库数据

public class User
{
    public int Id { get; set; }
    public string Username { get; set; }
    public string Email { get; set; }
}

public class ApplicationDbContext : DbContext
{
    public DbSet<User> Users { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("YourConnectionStringHere");
    }
}

public class UserService
{
    private readonly ApplicationDbContext _context;

    public UserService(ApplicationDbContext context)
    {
        _context = context;
    }

    public User OnSignedIn(string username)
    {
        return _context.Users.FirstOrDefault(u => u.Username == username);
    }
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<ApplicationDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

    services.AddScoped<UserService>();
}

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=your_server;Database=your_database;User Id=your_user;Password=your_password;"
  }
}

dotnet ef migrations add InitialCreate
dotnet ef database update

public User OnSignedIn(string username)
{
    return _context.Users
        .Where(u => u.Username == username)
        .FirstOrDefaultAsync().Result;
}