RestaurantSite_API/ProRestaurant/DBContexts/DBContext.cs

using Microsoft.EntityFrameworkCore;
using Npgsql;
using ProRestaurant.Models;
using ProRestaurant.Models.Accounts;
using ProRestaurant.Models.Restaurants;
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Threading.Tasks;

namespace ProRestaurant.DBContexts
{
    public class DBContext : DbContext
    {
        private string connectionString = "";
        private bool UseSQL = false;
        public DBContext(DbContextOptions<DBContext> options) 
            : base(options)
        {
            foreach (var extention in options.Extensions)
            {
                if (extention.GetType().ToString() == "Npgsql.EntityFrameworkCore.PostgreSQL.Infrastructure.Internal.NpgsqlOptionsExtension")
                {
                    connectionString = ((Npgsql.EntityFrameworkCore.PostgreSQL.Infrastructure.Internal.NpgsqlOptionsExtension)extention).ConnectionString;
                    UseSQL = false;
                }
                if (extention.GetType().ToString() == "Microsoft.EntityFrameworkCore.SqlServer.Infrastructure.Internal.SqlServerOptionsExtension")
                {
                    connectionString = ((Microsoft.EntityFrameworkCore.SqlServer.Infrastructure.Internal.SqlServerOptionsExtension)extention).ConnectionString;
                    UseSQL = true;
                }
            }
        }

        #region Accounts
        public DbSet<User> Users { get; set; }
        public DbSet<DriverDetail> DriverDetails { get; set; }
        public DbSet<UserAddress> UserAddresses { get; set; }
        #endregion

        #region Restaurants
        public DbSet<Restaurant> Restaurants { get; set; }
        public DbSet<TradingHours> TradingHours { get; set; }
        #endregion 

        public override int SaveChanges()
        {
            foreach (var item in ChangeTracker
                                    .Entries()
                                    .Where(x => x.State == EntityState.Modified || x.State == EntityState.Added)
                                    .Select(x => x.Entity)
                                    .ToList())
            {
                if (item is BaseObject)
                {
                    (item as BaseObject).UpdateModified(string.Empty);
                }
            }
            UpdateSoftDeleteStatuses();
            return base.SaveChanges();
        }

        private void UpdateSoftDeleteStatuses()
        {
            foreach (var entry in ChangeTracker.Entries())
            {
                switch (entry.State)
                {
                    case EntityState.Added:
                        entry.CurrentValues["IsDeleted"] = false;
                        break;
                    case EntityState.Deleted:
                        entry.State = EntityState.Modified;
                        entry.CurrentValues["IsDeleted"] = true;
                        break;
                }
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<User>().HasQueryFilter(m => EF.Property<bool>(m, "IsDeleted") == false);
            modelBuilder.Entity<UserAddress>().HasQueryFilter(m => EF.Property<bool>(m, "IsDeleted") == false);
            modelBuilder.Entity<DriverDetail>().HasQueryFilter(m => EF.Property<bool>(m, "IsDeleted") == false);
            modelBuilder.Entity<Restaurant>().HasQueryFilter(m => EF.Property<bool>(m, "IsDeleted") == false);
            modelBuilder.Entity<TradingHours>().HasQueryFilter(m => EF.Property<bool>(m, "IsDeleted") == false);
        }

        public int GetNextID(string tableName)
        {
            int returnValue = 0;
            if (!UseSQL)
            {
                NpgsqlConnection connection = new NpgsqlConnection(connectionString);
                connection.Open();

                NpgsqlCommand cmd = connection.CreateCommand();
                cmd.CommandText = string.Format("select MAX(\"Id\") from \"{0}\"", tableName);
                NpgsqlDataReader reader = cmd.ExecuteReader();                

                while (reader.Read())
                {
                    returnValue = int.Parse(reader[0] == null ? "0" : reader[0].ToString() == "" ? "0" : reader[0].ToString());
                }

                connection.Close();
            }
            else
            {
                SqlConnection connection = new SqlConnection(connectionString);
                connection.Open();

                SqlCommand cmd = connection.CreateCommand();
                cmd.CommandText = string.Format("select MAX(\"Id\") from \"{0}\"", tableName);
                SqlDataReader reader = cmd.ExecuteReader();                

                while (reader.Read())
                {
                    returnValue = int.Parse(reader[0] == null ? "0" : reader[0].ToString() == "" ? "0" : reader[0].ToString());
                }

                connection.Close();
            }
            return returnValue + 1;
        }
    }
}