覆盖SaveChanges()的最佳方法

Question

我们在一个项目上工作了1个月,有6个实体与其他实体没有任何关系.它们都是简单的实体.

我们为每个实体创建了6个不同的操作类.类的SaveOrUpdateEntity()方法几乎与您的想法相同.它是这样的:

public static ErrorType SaveOrUpdateEntity(Entity entity, int userID)
{
    try
    {
        using (DataEntities ctx = new DataEntities())
        {
            if (entity != null)
            {
                if (entity.entityID == 0)
                {
                    entity.CreateDate = DateTime.Now;
                    entity.CreatedBy = userID;

                    ctx.Entry(entity).State = EntityState.Added;
                }
                else
                {
                    entity.ModifyDate = DateTime.Now;
                    entity.ModifiedBy = userID;

                    ctx.Entry(entity).State = EntityState.Modified;
                }
            }

            ctx.SaveChanges();
        }

        return ErrorType.NoError;
    }
    catch (Exception ex)
    {
        return ErrorType.SaveError;
    }

}

如果SaveOrUpdateEntity()方法更短并且通过重写SaveChanges()方法更通用,那将非常有用.根据有关重写SaveChanges()方法的其他问题,文章和帖子,实现存储实体状态的接口是一个很好的解决方案,但我也想知道其他解决方案.

因为我是新手,所有答案都将非常感激.

谢谢.

Answer 1

你可以做到以下几点

1-在应用程序中创建一个接口,所有具有以下属性的类都将实现此接口:Id,CreatedDate,CreatedBy,ModifiedDate,ModifiedBy

public interface ITrack
{
      int Id{get; set;}
      int CreatedBy{get; set;}
      DateTime CreatedDate{get; set;}
      int? ModifiedBy{get; set;} // int? because at first add, there is no modification
      DateTime? ModifiedBy {get; set;}
}

最佳实践定义CreatedBy,并ModifiedBy为string这将是很好的性能和维护

2-添加一个TrackableEntry实现接口的类ITrack

public abstract class TrackableEntry : ITrack
{
      public int Id{get; set;}
      public int CreatedBy{get; set;}
      public DateTime CreatedDate{get; set;}
      public int? ModifiedBy{get; set;} 
      public DateTime? ModifiedBy {get; set;}
}

3-从所有类中删除界面中提到的属性,并让这些类直接从中实现 TrackableEntry

public class A: TrackableEntry
{
    //public int Id{get; set;}
    //public int CreatedBy{get; set;}
    //public DateTime CreatedDate{get; set;}
    //public int? ModifiedBy{get; set;}
    //public DateTime? ModifiedBy {get; set;}
}

4-在您的DbContext文件中覆盖您的SaveChanges和添加属性,UserId 或者UserName如果您遵循该*Best practices*部分

public int UserId{get; set;}

public override int SaveChanges()
{
    this.ChangeTracker.DetectChanges();
    var added = this.ChangeTracker.Entries()
                .Where(t => t.State == EntityState.Added)
                .Select(t => t.Entity)
                .ToArray();

    foreach (var entity in added)
    {
        if (entity is ITrack)
        {
            var track = entity as ITrack;
            track.CreatedDate = DateTime.Now;
            track.CreatedBy = UserId;
        }
    }

    var modified = this.ChangeTracker.Entries()
                .Where(t => t.State == EntityState.Modified)
                .Select(t => t.Entity)
                .ToArray();

    foreach (var entity in modified)
    {
        if (entity is ITrack)
        {
            var track = entity as ITrack;
            track.ModifiedDate = DateTime.Now;
            track.ModifiedBy = UserId;
        }
    }
    return base.SaveChanges();
}

当你想调用SaveChanges方法时,最后在你的表单中,确保你设置UserId或UserName值

var entities=new Entities(); // assuming that your DbContext file called Entities
// code for adding or deletion or modification here
entities.As.Add(new A(){...});

// ....

entities.UserId=MyUser;
entities.SaveChanges();

希望对你有帮助