SCHALE.GameServer/SCHALE.Common/Database/SCHALEContext.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using Microsoft.EntityFrameworkCore.ValueGeneration;
using MongoDB.EntityFrameworkCore.Extensions;
using SCHALE.Common.Database.Models;

namespace SCHALE.Common.Database
{
    public class SCHALEContext : DbContext
    {
        public DbSet<Account> Accounts { get; set; }
        public DbSet<Counter> Counters { get; set; }

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

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {

            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Account>().Property(x => x.Uid).HasValueGenerator<AccountAutoIncrementValueGenerator>();
            modelBuilder.Entity<Account>().ToCollection("accounts");
            modelBuilder.Entity<Counter>().ToCollection("counters");
        }
    }

    class AccountAutoIncrementValueGenerator : AutoIncrementValueGenerator
    {
        protected override string Collection => "account";
    }

    abstract class AutoIncrementValueGenerator : ValueGenerator<uint>
    {
        protected abstract string Collection { get; }
        public override bool GeneratesTemporaryValues => false;

        public override uint Next(EntityEntry entry)
        {
            if (entry.Context is not SCHALEContext)
            {
                throw new ArgumentNullException($"{nameof(AutoIncrementValueGenerator)} is only implemented for {nameof(SCHALEContext)}");
            }

            var context = ((SCHALEContext)entry.Context);
            var counter = context.Counters.SingleOrDefault(x => x.Id == Collection);

            if (counter is null)
            {
                counter = new Counter() { Id = Collection, Seq = 0 };
                context.Counters.Add(counter);
            }

            counter.Seq++;
            context.Update(counter);

            return counter.Seq;
        }
    }
}