// @nuget: Microsoft.EntityFrameworkCore.Sqlite -Version 6.0.0

// @nuget: Detached.Mappers.EntityFramework -Version 6.4.0

​

using System;

using System.Threading.Tasks;

using Detached.Mappers.EntityFramework;

using Microsoft.Data.Sqlite;

using Microsoft.EntityFrameworkCore; 

using System.Linq;

​

public class Program

{

    public static async Task Main()

    {

        using (TestDbContext dbContext = new TestDbContext())

        {

        await dbContext.Database.EnsureCreatedAsync();

​

        InvoiceType invoiceType = new InvoiceType

        {

          Id = 1,

          Name = "Type A"

        };

        dbContext.Add(invoiceType);

        await dbContext.SaveChangesAsync();

     }

​

        using (TestDbContext dbContext = new TestDbContext())

        {

            Invoice invoice = new Invoice

            {

                InvoiceType = new InvoiceType { Id = 1 }

            };

​

            dbContext.Entry(invoice).State = EntityState.Added;

            dbContext.Entry(invoice.InvoiceType).State = EntityState.Unchanged;

​

            await dbContext.SaveChangesAsync();

        }

​

        using (TestDbContext dbContext = new TestDbContext())

        {

            Invoice invoice = new Invoice

            {

                InvoiceType = await dbContext.FindAsync<InvoiceType>(1)

            };

​

            dbContext.Add(invoice); 

​

            await dbContext.SaveChangesAsync();

        }

​

        using (TestDbContext dbContext = new TestDbContext())

        {

            var invoice = await dbContext.Invoices.Include(i => i.InvoiceType).FirstOrDefaultAsync();

​

            await dbContext.Invoices.Where(i => i.InvoiceType.Id == 1).FirstOrDefaultAsync();

​

            Console.WriteLine($"Associated invoice type is: '{invoice.InvoiceType.Name}'");

        }

    }

​

    class TestDbContext : DbContext

    {

        static SqliteConnection _connection;

​

        static TestDbContext()

        {

            _connection = new SqliteConnection($"DataSource=file:{Guid.NewGuid()}?mode=memory&cache=shared");

            _connection.Open();

        }

​

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        {

            optionsBuilder.UseSqlite(_connection).UseMapping();

        }

​

        public DbSet<Invoice> Invoices { get; set; }

    }

​

    class Invoice

    {

        public int Id { get; set; }

​

        public string Subject { get; set; }

​

        public DateTime InvoiceDate { get; set; }

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        public DateTime DueDate { get; set; }

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        public InvoiceType InvoiceType { get; set; }

    }

​

    class InvoiceType

    {

        public int Id { get; set; }

​

        public string Name { get; set; }

    }

}