保存更改时设置默认值

Question

我所有的实体都扩展了 BaseEntity，它具有那些（相关）属性：

namespace Sppd.TeamTuner.Core.Domain.Entities
{
    public abstract class BaseEntity
    {
        /// <summary>
        ///     Unique identifier identifying a single instance of an entity.
        /// </summary>
        public Guid Id { get; set; }

        /// <summary>
        ///     Specifies when the entity instance has been created.
        /// </summary>
        public DateTime CreatedOnUtc { get; set; }

        /// <summary>
        ///     Specifies by whom the entity instance has been created.
        /// </summary>
        public Guid CreatedById { get; set; }

        /// <summary>
        ///     Specifies when the entity instance has been last updated.
        /// </summary>
        public DateTime ModifiedOnUtc { get; set; }

        /// <summary>
        ///     Specifies by whom the entity instance has been last modified.
        /// </summary>
        public Guid ModifiedById { get; set; }

        protected BaseEntity()
        {
            Id = Guid.NewGuid();
        }
    }
}

我想让 ef 在保存前设置 created/modified 属性。为此，我在配置 DbContext 时添加了以下内容：

    private void ConfigureBaseEntity<TEntity>(EntityTypeBuilder<TEntity> builder)
        where TEntity : BaseEntity
    {
        // Constraints
        builder.Property(e => e.CreatedOnUtc)
               .HasDefaultValueSql(_databaseConfig.Value.SqlUtcDateGetter)
               .ValueGeneratedOnAdd();
        builder.Property(e => e.ModifiedOnUtc)
               .HasDefaultValueSql(_databaseConfig.Value.SqlUtcDateGetter)
               .ValueGeneratedOnAddOrUpdate()
               .IsConcurrencyToken();
        builder.Property(e => e.CreatedById)
               .HasValueGenerator<CurrentUserIdValueGenerator>()
               .ValueGeneratedOnAdd();
        builder.Property(e => e.ModifiedById)
               .HasValueGenerator<CurrentUserIdValueGenerator>()
               .ValueGeneratedOnAddOrUpdate();
    }

还有这个ValueGenerator：

internal class CurrentUserIdValueGenerator : ValueGenerator<Guid>
{
    public override bool GeneratesTemporaryValues => false;

    public override Guid Next(EntityEntry entry)
    {
        return GetCurrentUser(entry).Id;
    }

    private static ITeamTunerUser GetCurrentUser(EntityEntry entry)
    {
        var userProvider = entry.Context.GetService<ITeamTunerUserProvider>();
        if (userProvider.CurrentUser != null)
        {
            return userProvider.CurrentUser;
        }

        if (entry.Entity is ITeamTunerUser user)
        {
            // Special case for user creation: The user creates himself and thus doesn't exist yet. Use him as the current user.
            return user;
        }

        throw new BusinessException("CurrentUser not defined");
    }
}

通过在 DbContext 上调用 SaveChanges() 来保留更改时，出现以下异常：

Microsoft.EntityFrameworkCore.DbUpdateException
  HResult=0x80131500
  Message=An error occurred while updating the entries. See the inner exception for details.
  Source=Microsoft.EntityFrameworkCore.Relational
  StackTrace:
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.Execute(IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(DbContext _, ValueTuple`2 parameters)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChanges(IReadOnlyList`1 entries)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IReadOnlyList`1 entriesToSave)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Sppd.TeamTuner.Infrastructure.DataAccess.EF.TeamTunerContext.SaveChanges(Boolean acceptAllChangesOnSuccess) in E:\dev\Sppd.TeamTuner\Backend\Sppd.TeamTuner.DataAccess.EF\TeamTunerContext.cs:line 48

Inner Exception 1:
SqlException: Cannot insert the value NULL into column 'ModifiedById', table 'Sppd.TeamTuner-DEV.dbo.CardType'; column does not allow nulls. UPDATE fails.
The statement has been terminated.

检查 ChangeTracker 的内容时，所有实体都设置了 ModifiedById：旁注：ToList() 是必需的，否则它没有正确枚举

除了 ID 包含我期望的值这一事实外，ModifiedById 属性不可为空，因此永远不应为空（它可能包含 default(Guid)）。

知道发生了什么吗？

[编辑] 要添加的代码：

播种者：

internal class CardTypeDbSeeder : IDbSeeder
{
    private readonly IRepository<CardType> _cardTypeRepository;

    public CardTypeDbSeeder(IRepository<CardType> cardTypeRepository)
    {
        _cardTypeRepository = cardTypeRepository;
    }

    public int Priority => SeederConstants.Priority.BASE_DATA;

    public void Seed()
    {
        _cardTypeRepository.Add(new CardType
                                {
                                    Id = Guid.Parse(TestingConstants.CardType.ASSASSIN_ID),
                                    Name = "Assassin"
                                });
    }
        [...]
}

存储库：

namespace Sppd.TeamTuner.Infrastructure.DataAccess.EF.Repositories
{
    internal class Repository<TEntity> : IRepository<TEntity>
        where TEntity : BaseEntity
    {
        protected DbSet<TEntity> Set => Context.Set<TEntity>();

        protected TeamTunerContext Context { get; }

        protected virtual Func<IQueryable<TEntity>, IQueryable<TEntity>> Includes { get; } = null;

        public Repository(TeamTunerContext context)
        {
            Context = context;
        }

        public async Task<TEntity> GetAsync(Guid entityId)
        {
            TEntity entity;
            try
            {
                entity = await GetQueryWithIncludes().SingleAsync(e => e.Id == entityId);
            }
            catch (InvalidOperationException)
            {
                throw new EntityNotFoundException(typeof(TEntity), entityId.ToString());
            }

            return entity;
        }

        public async Task<IEnumerable<TEntity>> GetAllAsync()
        {
            return await GetQueryWithIncludes().ToListAsync();
        }

        public void Delete(Guid entityId)
        {
            var entityToDelete = GetAsync(entityId);
            entityToDelete.Wait();
            Set.Remove(entityToDelete.Result);
        }

        public void Add(TEntity entity)
        {
            Set.Add(entity);
        }

        public void Update(TEntity entity)
        {
            Set.Update(entity);
        }

        protected IQueryable<TEntity> GetQueryWithIncludes()
        {
            return Includes == null
                ? Set
                : Includes(Set);
        }
    }
}

提交更改：

            if (isNewDatabase)
            {
                s_logger.LogDebug($"New database created. Seed data for SeedMode={databaseConfig.SeedMode}");

                foreach (var seeder in scope.ServiceProvider.GetServices<IDbSeeder>().OrderBy(seeder => seeder.Priority))
                {
                    seeder.Seed();
                    s_logger.LogDebug($"Seeded {seeder.GetType().Name}");
                }

                // The changes are usually being saved by a unit of work. Here, while starting the application, we will do it on the context itself.
                context.SaveChanges();
            }

Answer 1

正如 GitHub 问题中的评论和大量浏览所讨论的那样，事实证明不可能为此使用价值生成器。我已经通过在 Datacontext.SaveChanges 的覆盖中实现 PrepareSaveChanges() 来解决它，它调用以下代码：

    private void SetModifierMetadataProperties(EntityEntry<BaseEntity> entry, DateTime saveDate)
    {
        var entity = entry.Entity;
        var currentUserId = GetCurrentUser(entry).Id;

        if (entity.IsDeleted)
        {
            entity.DeletedById = currentUserId;
            entity.DeletedOnUtc = saveDate;
            return;
        }

        if (entry.State == EntityState.Added)
        {
            entity.CreatedById = currentUserId;
            entity.CreatedOnUtc = saveDate;
        }

        entity.ModifiedById = currentUserId;
        entity.ModifiedOnUtc = saveDate;
    }

对于完整的实现，请遵循 SaveChangesAsync

覆盖的执行路径

保存更改时设置默认值

Set default value when saving changes

c#

entity-framework-core

ef-fluent-api

.net-core-2.2