EF核心变更跟踪-原始值和变更值出现问题

Question

我已将Net core API配置为.net core 2.0和EF core 2.0。它包含存储库模式架构。

现在，我正在尝试使用EF更改跟踪器为每个保存更改实施审核日志。

我的问题：每当我尝试为编辑/修改端点添加日志时，原始值和当前值都保持不变，并且是新近更新的值。因此，我无法跟踪修改或更改。

这是我的ApplicationContext文件，在其中我已重写保存调用。

 public class ApplicationContext : DbContext
{
    public ApplicationContext(DbContextOptions options) : base(options: options) { }

    public DbSet<Item> Item { get; set; }
    public DbSet<ChangeLog> ChangeLog { get; set; }        

    public override int SaveChanges()
    {
        var modifiedEntities = ChangeTracker.Entries();

        foreach (var change in modifiedEntities)
        {
            var entityType = change.Entity.GetType().Name;
            if (entityType == "LogItem")
                continue;

            if (change.State == EntityState.Modified)
            {
                foreach (var prop in change.OriginalValues.Properties)
                {
                    var id = change.CurrentValues["Id"].ToString();

                    //here both originalValue and currentValue  are same and it's newly updated value 
                    var originalValue = change.OriginalValues[prop]?.ToString();
                    var currentValue = change.CurrentValues[prop]?.ToString();
                    if (originalValue != currentValue)
                    {
                        ChangeLog.Add(
                            new ChangeLog()
                            {
                                CreationDateTime = DateTime.Now,
                                CreationUserId = 1,
                                Log = $"Edited item named {prop.Name} in {entityType} Id {id}.",
                                OldValue = originalValue,
                                NewValue = currentValue,
                                TableName = entityType,
                                FieldName = prop.Name
                            }
                        );
                    }
                }
            }
        }
        return base.SaveChanges();
    }
}

这是我的基本存储库。

public class EntityBaseRepository<T> : IEntityBaseRepository<T> where T : class, IFullAuditedEntity, new()
{
    private readonly ApplicationContext context;

    public EntityBaseRepository(ApplicationContext context)
    {
        this.context = context;
    }

    public virtual T GetSingle(int id) => context.Set<T>().AsNoTracking().FirstOrDefault(x => x.Id == id);

    public virtual T Add(T entity) => Operations(entity: entity, state: EntityState.Added);

    public virtual T Update(T entity) => Operations(entity: entity, state: EntityState.Modified);

    public virtual T Delete(T entity) => Operations(entity: entity, state: EntityState.Deleted);

    public virtual T Operations(T entity, EntityState state)
    {
        EntityEntry dbEntityEntry = context.Entry<T>(entity);

        if (state == EntityState.Added)
        {
            entity.CreationDateTime = DateTime.UtcNow;
            entity.CreationUserId = 1;

            context.Set<T>().Add(entity);
            dbEntityEntry.State = EntityState.Added;
        }
        else if (state == EntityState.Modified)
        {
            entity.LastModificationDateTime = DateTime.UtcNow;
            entity.LastModificationUserId = 1;

            //var local = context.Set<T>().Local.FirstOrDefault(entry => entry.Id.Equals(entity.Id));
            //if (local != null)
            //{
            //    context.Entry(local).State = EntityState.Detached;
            //}

            dbEntityEntry.State = EntityState.Modified;
        }
        else if (state == EntityState.Deleted)
        {
            entity.DeletionFlag = true;
            entity.DeletionUserId = 1;
            entity.DeletionDateTime = DateTime.UtcNow;

            dbEntityEntry.State = EntityState.Modified;
        }

        return entity;
    }

    public virtual void Commit() => context.SaveChanges();

}

最后是我的控制器，带有放置端点。

[Produces("application/json")]
[Route("api/Item")]
public class ItemController : Controller
{
    private readonly IItemRepository repository;
    private readonly IChangeLogRepository changeLogRepository;
    private readonly IMapper mapper;

    public ItemController(IItemRepository repository, IChangeLogRepository _changeLogRepository, IMapper mapper)
    {
        this.repository = repository;
        this.changeLogRepository = _changeLogRepository;
        this.mapper = mapper;
    }

    [HttpPut]
    public IActionResult Put([FromBody]ItemDto transactionItemDto)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        if (transactionItemDto.Id <= 0)
        {
            return new NotFoundResult();
        }

        Item item = repository.GetSingle(transactionItemDto.Id); //find entity first

        if (item == null)
        {
            return new NotFoundResult();
        }

        //map all the properties and commit
        var entity = mapper.Map<Item>(transactionItemDto);
        var updatedItem = repository.Update(entity);
        repository.Commit();

        return new OkObjectResult(mapper.Map<Item, ItemDto>(source: updatedItem));
    }
}

我不确定我在哪里做错什么，我尝试用SO来检查这种情况，但是没有运气。任何帮助将不胜感激，谢谢。

Answer 1

我想我看到您的代码有问题。在您的控制器中：

    //map all the properties and commit
    var entity = mapper.Map<Item>(transactionItemDto);
    var updatedItem = repository.Update(entity);
    repository.Commit();

在该代码中，您正在获取DTO并将其映射到Item的新实例。该Item的新实例知道当前数据库值的nothing，这就是为什么您在OriginalValue和CurrentValue中看到相同的新值的原因。

如果重复使用在此行中获得的Item item变量：

Item item = repository.GetSingle(transactionItemDto.Id); //find entity first

注意，您需要获取具有跟踪功能的实体，而不是存储库GetSingle如何通过AsNoTracking实现它。如果您使用该项目（现在具有原始/当前数据库值，则将您的transactionItemDto属性映射到该项目上，如下所示：

var entityToUpdate = mapper.Map<ItemDto, Item>(transactionItemDto);

然后，当您调用将它传递给EntityToUpdate的repository.Update方法时，我相信您会看到正确的前后值。

。。。。

我最初发布的

旧（错误）答案：在您的ApplicationContext代码中，您具有以下循环

foreach (var prop in change.OriginalValues.Properties)

我相信这是导致您的原始值/当前值相同的原因，因为您正在遍历原始值属性。尝试将该循环更改为：

foreach (var prop in change.Properties)

然后，尝试通过prop变量读取每个属性的值，如下所示：

var currentValue = prop.CurrentValue;
var originalValue = prop.OriginalValue;

编辑：啊-我现在看到在您的代码中，您正在尝试从change.OriginalValues集合中读取原始值，所以我认为这无济于事。

Answer 2

我没有使用存储库模式，但是我为EF Core 2.1实现了非常相似的审核日志。我遍历实体框架变更跟踪器正在追踪的变更列表，并将其记录下来。

我注意到，当我想更新实体时，有两种方法可以做到。一种是我从数据库中读取现有实体，重新分配变量，然后保存它。第二种方法是简单地创建一个对象，将其附加到数据库上下文，然后将要更新的属性设置为修改后的状态。当我这样做时，我的审核将无法使用原始值，因为原始值从未真正从数据库中读取过。

示例：

//auditing works fine
var myEntity = await db.MyEntity.FindAsync(entityId);
myEntity.Property = newValue;
await db.SaveChangesAsync();

//auditing can't track the old value
var myEntity = new MyEntity();
db.Attach(myEntity);
myEntity.Property = newValue;
await db.SaveChangesAsync();

例如，这是我的审核代码的重要部分

foreach (var entity in db.ChangeTracker.Entries())
{
    if(entity.State == EntityState.Detached || entity.State == EntityState.Unchanged)
    {
        continue;
    }

    var audits = new List<Audit>();

    //the typeId is a string representing the primary keys of this entity.
    //this will not be available for ADDED entities with generated primary keys, so we need to update those later
    string typeId;

    if (entity.State == EntityState.Added && entity.Properties.Any(prop => prop.Metadata.IsPrimaryKey() && prop.IsTemporary))
    {
        typeId = null;
    }
    else
    {
        var primaryKey = entity.Metadata.FindPrimaryKey();
        typeId = string.Join(',', primaryKey.Properties.Select(prop => prop.PropertyInfo.GetValue(entity.Entity)));
    }

    //record an audit for each property of each entity that has been changed
    foreach (var prop in entity.Properties)
    {
        //don't audit anything about primary keys (those can't change, and are already in the typeId)
        if(prop.Metadata.IsPrimaryKey() && entity.Properties.Any(p => !p.Metadata.IsPrimaryKey()))
        {
            continue;
        }

        //ignore values that won't actually be written
        if(entity.State != EntityState.Deleted && entity.State != EntityState.Added && prop.Metadata.AfterSaveBehavior != PropertySaveBehavior.Save)
        {
            continue;
        }

        //ignore values that won't actually be written
        if (entity.State == EntityState.Added && prop.Metadata.BeforeSaveBehavior != PropertySaveBehavior.Save)
        {
            continue;
        }

        //ignore properties that didn't change
        if(entity.State == EntityState.Modified && !prop.IsModified)
        {
            continue;
        }

        var audit = new Audit
        {
            Action = (int)entity.State,
            TypeId = typeId,
            ColumnName = prop.Metadata.SqlServer().ColumnName,
            OldValue = (entity.State == EntityState.Added || entity.OriginalValues == null) ? null : JsonConvert.SerializeObject(prop.OriginalValue),
            NewValue = entity.State == EntityState.Deleted ? null : JsonConvert.SerializeObject(prop.CurrentValue)
        };
    }

    //Do something with audits
}