Реализация интерфейса IPersistedGrantStore (IdentityServer4)

Всем привет. Я пытаюсь сохранить модифицировать свою программу и сохранять токен не в памяти, а в БД. Для этого я решил реализовать интерфейс IPersistedGrantStore. Сейчас я реализовал все 5 методов. Но есть ощущение, что с ошибками. Можете ли подсказать верную реализацию для этих методов?

using AutoMapper;
using IdentityServer4.Models;
using IdentityServer4.Services;
using IdentityServer4.Stores;
using Microsoft.Extensions.Logging;
using Microsoft.IdentityModel.Tokens;
using ServiceStack;
using ServiceStack.Data;
using ServiceStack.OrmLite;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace innRoad.Pms.Identity.Api.Core.DataAccess
{
    public class IdentityPersistedGrantStore : IPersistedGrantStore
    {
        private readonly IDbConnectionFactory _dbConnectionFactory;
        private readonly ILogger logger;

        public IdentityPersistedGrantStore(IDbConnectionFactory dbConnectionFactory)
        {
            _dbConnectionFactory = dbConnectionFactory;
            this.logger = logger;
        }

        public async Task<IEnumerable<PersistedGrant>> GetAllAsync(PersistedGrantFilter filter) 
        {
            IEnumerable<PersistedGrantEntity> persistedGrantEntities;

            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                persistedGrantEntities = await identityConnection.LoadSelectAsync<PersistedGrantEntity>(x => x.SubjectId == filter.SubjectId);
            }

            return MapPersistedEntityToPersistedGrant(persistedGrantEntities);
        }

        public async Task<PersistedGrant> GetAsync(string key)
        {
            IEnumerable<PersistedGrantEntity> persistedGrantEntities;

            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                persistedGrantEntities = await identityConnection.LoadSelectAsync<PersistedGrantEntity>(x => x.Id.Equals(key));
            }

            return MapPersistedGrant(persistedGrantEntities.FirstOrDefault());
        }

        public async Task RemoveAllAsync(PersistedGrantFilter filter)
        {
            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                await identityConnection.DeleteAsync<PersistedGrantEntity>(x =>
                x.ClientId == filter.ClientId &&
                x.SubjectId == filter.SubjectId);
            }
        }

        public async Task RemoveAsync(string key)
        {
            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                await identityConnection.DeleteAsync<PersistedGrantEntity>(x => x.Id == key);
            }
        }

        public async Task StoreAsync(PersistedGrant grant)
        {
            grant.Key = EncodePersistedGrantKey(grant.Key);
            var persistedGrantEntity = MapPersistedGrants(grant);
            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                identityConnection.CreateTable<PersistedGrantEntity>();
                await identityConnection.InsertAsync(persistedGrantEntity);
            }
        }

        private PersistedGrantEntity MapPersistedGrants(PersistedGrant grant)
        {
            return new PersistedGrantEntity
            {
                Id = grant.Key,
                ClientId = grant.ClientId,
                SessionId = grant.SessionId,
                ConsumedTime = grant.ConsumedTime,
                CreationTime = grant.CreationTime,
                Expiration = grant.Expiration,
                Data = grant.Data,
                Description = grant.Description,
                SubjectId = grant.SubjectId,
                Type = grant.Type
            };
        }

        private string EncodePersistedGrantKey(string key)
        {
            key = Base64UrlEncoder.Encode(key);
            return key;
        }

        private PersistedGrant MapPersistedGrant(PersistedGrantEntity persistedGrantEntity)
        {
            return new PersistedGrant
            {
                Key = persistedGrantEntity.Id,
                ClientId = persistedGrantEntity.ClientId,
                SessionId = persistedGrantEntity.SessionId,
                ConsumedTime = persistedGrantEntity.ConsumedTime,
                CreationTime = persistedGrantEntity.CreationTime,
                Expiration = persistedGrantEntity.Expiration,
                Data = persistedGrantEntity.Data,
                Description = persistedGrantEntity.Description,
                SubjectId = persistedGrantEntity.SubjectId,
                Type = persistedGrantEntity.Type
            };
        }

        private IEnumerable<PersistedGrant> MapPersistedEntityToPersistedGrant(IEnumerable<PersistedGrantEntity> persistedGrantEntities)
        {
            var persistedGrant = new List<PersistedGrant>();

            foreach (var entityPersistedGrant in persistedGrantEntities)
            {
                var persisted = new PersistedGrant
                {
                    Key = entityPersistedGrant.Id,
                    Type = entityPersistedGrant.Type,
                    SubjectId = entityPersistedGrant.SubjectId,
                    SessionId = entityPersistedGrant.SessionId,
                    ClientId = entityPersistedGrant.ClientId,
                    Description = entityPersistedGrant.Description,
                    CreationTime = entityPersistedGrant.CreationTime,
                    Expiration = entityPersistedGrant.Expiration,
                    ConsumedTime = entityPersistedGrant.ConsumedTime,
                    Data = entityPersistedGrant.Data
                };
                persistedGrant.Add(persisted);
            }

            return persistedGrant;
        }
    }
}

На данный момент в методе GetAsync я получаю такую ошибку: Conversion failed when converting the varchar value '2jfZz' to data type int.

public async Task<PersistedGrant> GetAsync(string key)
        {
            IEnumerable<PersistedGrantEntity> persistedGrantEntities;

            using (var identityConnection = await _dbConnectionFactory.OpenAsync(DbConnectionNames.Identity))
            {
                persistedGrantEntities = await identityConnection.LoadSelectAsync<PersistedGrantEntity>(x => x.Id.Equals(key));
            }

            return MapPersistedGrant(persistedGrantEntities.FirstOrDefault());
        }

Хотя я не вижу тут явной конвертации в int. Скорее всего я просто неверно реализовал этот метод. Ошибка в этой строке:

persistedGrantEntities = await identityConnection.LoadSelectAsync<PersistedGrantEntity>(x => x.Id.Equals(key));