DiunaBI/WebAPI/AppDbContext.cs

using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using WebAPI.Models;

namespace WebAPI
{
    public class AppDbContext : DbContext
    {
        public DbSet<User> Users { get; set; }
        public DbSet<Layer> Layers { get; set; }
        public DbSet<Record> Records { get; set; }
        public DbSet<ProcessSource> ProcessSources { get; set; }

        public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<ProcessSource>().HasKey(x => new
            {
                x.LayerId,
                x.SourceId
            });
        }

        public static readonly Microsoft.Extensions.Logging.LoggerFactory _myLoggerFactory =
            new LoggerFactory(new[] {
                new Microsoft.Extensions.Logging.Debug.DebugLoggerProvider()
        });

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseLoggerFactory(_myLoggerFactory);
        }
    }
}