presence/Demo/Data/RemoteData/RemoteDataBase/RemoteDatabaseContext.cs

using Microsoft.EntityFrameworkCore;
using Demo.Data.RemoteData.RemoteDataBase.DAO;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace Demo.Data.RemoteData.RemoteDataBase
{
    public class RemoteDatabaseContext: DbContext
    {
        public DbSet<GroupDao> Groups { get; set; }
        public DbSet<UserDao> Users { get; set; }
        public DbSet<PresenceDao> PresenceDaos { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseNpgsql("Host=localhost;Port=5432;Database=presencedb;Username=postgres;Password=123;Include Error Detail=True;");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<GroupDao>().HasKey(group=>group.Id);
            modelBuilder.Entity<GroupDao>().Property(group => group.Id).ValueGeneratedOnAdd();
            modelBuilder.Entity<UserDao>().HasKey(user=>user.UserId);
            modelBuilder.Entity<UserDao>().Property(user=>user.UserId).ValueGeneratedOnAdd();
            modelBuilder.Entity<PresenceDao>().HasKey(presence => new
            {
                presence.UserId,
                presence.Date,
                presence.IsAttedance,
                presence.LessonNumber
            });
                
        }
    }
}