c# - Linq to SQL 通用存储库模式更新问题

Question

我有一个奇怪的问题。我正在使用通用存储库模式和 Linq to SQL。我在对象之间有很多对多的关系，这些对象是 dbml 生成的对象，这就是问题所在。当我尝试更新 Player 对象时出现错误。当我尝试更新玩家技能名称时发生错误。这是我遇到的异常:

An exception of type 'System.InvalidOperationException' occurred in System.Data.Linq.dll but was not handled in user code

Additional information: An attempt was made to remove a relationship between a Skill and a PlayerSkill. However, one of the relationship's foreign keys (PlayerSkill.Skill_ID) cannot be set to null.

这是更新方法。

 public void Update(PlayerEntity player)
    {
        Player p = Mapper.Map<PlayerEntity, Player>(player);
        _unitOfWork.SkillRepository.AddOrUpdate(p.PlayerSkills.Select(i => i.Skill).ToList());
        _unitOfWork.ProfileRepository.AddOrUpdate(p.Profile);
        _unitOfWork.SocialAccountRepository.AddOrUpdate(p.SocialAccount);
        _unitOfWork.PlayerRepository.AddOrUpdate(p);
    }

AddOrUpdate repo 方法:

public void AddOrUpdate(ICollection<TEntity> entities)
    {
        foreach (var e in entities)
        {
            AddOrUpdate(e);
        }
    }

public void AddOrUpdate(TEntity entity)
    {
        if (GetPrimaryKeyValue(entity) > 0)
        {
            Update(entity);
        }
        else
        {
            Insert(entity);
        }
    }

DataLINQ层上的Update方法

public void Update(TEntity entity)
    {
        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        var original = GetById(GetPrimaryKeyValue(entity));

        ApplyChanges(original, entity);

        _context.SubmitChanges();
    }

最后; ApplyChanges

private void ApplyChanges<F, S>(F originalEntity, S newEntity)
    {
        var entityType = typeof(F);
        var entityProperties = entityType.GetProperties();
        foreach (var propertyInfo in entityProperties)
        {
            var currentProperty = entityType.GetProperty(propertyInfo.Name);
            currentProperty.SetValue(originalEntity, propertyInfo.GetValue(newEntity, null));
        }
    }

我调用对象如下:

public IHttpActionResult PutPlayer(int id, PlayerEntity player)
    {
        if (player == null)
        {
            return NotFound();
        }
        _playerService.Update(player);

        return Ok();
    }

注意:我使用AutoMapper来映射对象，但我认为这与错误无关。提前致谢。

Answer 1

问题是您的方法 ApplyChanges 复制了太多属性。您希望它仅复制标量属性，即 int、string 等类型的属性，而不是引用和集合。但是您的方法可以完成所有这些操作。

这会导致 LINQ-to-SQL 断定 PlayerSkills 已被全新的 PlayerSkill 对象集合所取代。所以它会尝试插入新的。但它也会尝试孤立现有的。这会导致 PlayerSkill.Skill_ID 无法设置为 null 的异常。

解决方案是只复制标量属性:

private void ApplyChanges<F, S>(F originalEntity, S newEntity)
{
    var entityType = typeof(F);
    var entityProperties = entityType.GetProperties();
    foreach (var propertyInfo in entityProperties
        // Filter scalar properties
        .Where(pi => pi.PropertyType.IsValueType || pi.PropertyType == typeof(string)))
    {
        var currentProperty = entityType.GetProperty(propertyInfo.Name);
        currentProperty.SetValue(originalEntity, propertyInfo.GetValue(newEntity, null));
    }
}

过滤值类型属性和字符串属性(字符串不是值类型而是类)