EffectiveTask/DeliveryWebApi/Model/DeliveryDbContext.cs

using System.Collections.Immutable;
using Microsoft.EntityFrameworkCore;

namespace DeliveryWebApi.Model;

public class DeliveryDbContext(DbContextOptions<DeliveryDbContext> options) : DbContext(options)
{
    public DbSet<District> Districts { get; init; }
    public DbSet<Order> Orders { get; init; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<District>()
            .HasMany(d => d.Orders)
            .WithOne(o => o.District)
            .HasForeignKey(o => o.DistrictId)
            .IsRequired();
        
        modelBuilder.Entity<District>()
            .HasIndex(d => d.Name)
            .IsUnique();
        
        // random districts
        var districtNames = new List<string>
        {
            "Viborgskiy", "Primorskiy", "Kalininskiy", "Petrogradskiy", "Center", "Admiralteyskiy", "Vasileostrovskiy",
            "Kirovskiy", "Krasnoselskiy", "Moskovskiy", "Frunzenskiy", "Nevskiy", "Krasnogvardeyskiy", "Kolpinskiy",
            "Pushkinskiy", "Pavlovskiy", "Petrodvortsoviy", "Lomonosovskiy", "Kurortniy", "Kronshtadskiy"
        };
        modelBuilder.Entity<District>()
            .HasData(districtNames.Select((n, i) => new District { Id = i + 1, Name = n }));
        
        // random orders
        var rnd = new Random();
        var startDate = new DateTime(2020, 1, 1);
        var range = (DateTime.Today - startDate).Days;
        modelBuilder.Entity<Order>()
            .HasData(Enumerable.Range(1, 100).Select(i =>
            {
                var districtId = rnd.Next(0, districtNames.Count) + 1;
                var weight = rnd.NextSingle() * 10 + 0.1f;
                var date = startDate.AddDays(rnd.Next(range));
                return new Order { Id = i, DistrictId = districtId, Weight = weight, DeliveryDate = date };
            }));
    }
}