NRE when adding property named "Count" to a property bag entity type

[AndriySvyryd]

Originally filed at PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#1491

This seems to be a bug in EF Core that is only triggered for specific entity property names (e.g. when your property is named Count) in migration snapshots.

The underlying issue seems to be, that EF Core is checking the properties of the wrong type. It does enumerated the properties of the Metadata.ClrType property, but it is not set to the actual entity type (since this is a migration snapshot), but to a type of Dictionary<string, object>.
It then hits the Count property of this Dictionary<string, object>, checks its int type against the expected double type of the entity's property, realizes that they do not match, and finally returns null, which will then throws the NRE.

This is the line with the issue:

efcore/src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs

Line 579 in 159c7e7

memberInfo ??= Metadata.ClrType.GetMembersInHierarchy(propertyName).FirstOrDefault();

memberInfo ??= Metadata.ClrType.GetMembersInHierarchy(propertyName).FirstOrDefault();

---

@AndriySvyryd, @ajcvickers Reproduced with the following code:

Program.cs

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

namespace IssueConsoleTemplate
{
    public class RegistryOrderServices
    {
        public Guid Id { get; set; }
        public double Count { get; set; }
    }

    public class Context : DbContext
    {
        public DbSet<RegistryOrderServices> RegistryOrderServices { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                var connectionString = "server=127.0.0.1;port=3308;user=root;password=;database=Issue1491";
                var serverVersion = ServerVersion.AutoDetect(connectionString);

                optionsBuilder.UseMySql(connectionString, serverVersion)
                    .UseLoggerFactory(
                        LoggerFactory.Create(
                            b => b
                                .AddConsole()
                                .AddFilter(level => level >= LogLevel.Information)))
                    .EnableSensitiveDataLogging()
                    .EnableDetailedErrors();
            }
        }
    }

    internal static class Program
    {
        private static void Main()
        {
        }
    }
}

Add an initial migration and then another one (can be empty).
Should be reproducible with any provider.

[war-beast]

The same thing happen with a property named "Values"