GazpromApp/Utils/AppDbContext.cs

using Microsoft.EntityFrameworkCore;
using GazpromApp.Models;

namespace GazpromApp.Utils;

public class AppDbContext : DbContext
{
    public DbSet<Models.Image> Image { get; set; }
    public DbSet<Equipment> Equipment { get; set; }
    public DbSet<Models.Point> Point { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        base.OnConfiguring(optionsBuilder);
        optionsBuilder.UseSqlite("Data Source=MainDB.db");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        // Images
        modelBuilder.Entity<Models.Point>()
            .HasMany(e => e.Images)
            .WithMany(e => e.Points);

        modelBuilder.Entity<Equipment>()
            .HasOne(e => e.Image)
            .WithMany(e => e.Equipment)
            .HasForeignKey(e => e.ImageId);

        // Properties
        modelBuilder.Entity<Models.Point>()
            .HasMany(e => e.Properties)
            .WithMany(e => e.Points);

        modelBuilder.Entity<Equipment>()
            .HasMany(e => e.Properties)
            .WithMany(e => e.Equipment);

        // Equipment
        modelBuilder.Entity<Equipment>()
            .HasOne(e => e.Point)
            .WithMany(e => e.Equipment)
            .HasForeignKey(e => e.PointId);
    }
}