How do I resolve this error in .NET Minimal API integration with PostgreSQL? – Asp.net

I am trying to make APIs using ASP.Net Minimal API thingy and I am trying to use PostgreSQL as Database so for that I am following an Article and and I have followed it so far but I am unable to get desired output.

I have provided all the files below from my Project…

Program.cs

using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");

builder.Services.AddDbContext<BookStoreDB>(options => options.UseNpgsql(connectionString));

builder.Services.AddDatabaseDeveloperPageExceptionFilter();

var app = builder.Build();

app.MapGet("/", () =>
{
    return "Hello World";
});

app.MapPost("/register", (BookStoreDB database, RegisterRequest body, HttpResponse response) =>
{
    User user = new User(1);
    user.FirstName = body.firstName;
    user.LastName = body.lastName;
    user.Email = body.email;
    user.Password = body.password;
    database.Users.Add(user);
    database.SaveChanges();
    response.StatusCode = 201;
    return new { requestBody = body };
});

appsettings.json

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=localhost;Port=5432;Database=BookStore;User=postgres;Password=somepass"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

BookStoreDB.cs

using Microsoft.EntityFrameworkCore;

public class BookStoreDB : DbContext
{
    public BookStoreDB(DbContextOptions<BookStoreDB> options) : base(options)
    {

    }

    public DbSet<User> Users => Set<User>();
}

RequestObjects.cs

public class LoginRequest
{
    public string email { get; set; } = default!;
    public string password { get; set; } = default!;
}

public class RegisterRequest
{
    public string firstName { get; set; } = default!;
    public string lastName { get; set; } = default!;
    public string email { get; set; } = default!;
    public string password { get; set; } = default!;
}

User.cs

public record User(int id)
{
    public string FirstName { get; set; } = default!;
    public string LastName { get; set; } = default!;
    public string Email { get; set; } = default!;
    public string Password { get; set; } = default!;
}

I don’t have any Idea what these files are for and the convention about them. But when I run the Project using dotnet watch run it starts successfully but whenever I try to make an POST request on /register route , I get an Error shown below…