型号OnDelete事件？ [英] Model OnDelete event?

问题描述

我有一个简单的模型，看起来像这样：

I've got a simple model that looks like this:

public class ImageFile
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public ImageMeta Meta { get; set; }
    public string FileName { get; set; }
    public DateTime DateUploaded { get; set; }
    public int Width { get; set; }
    public int Height { get; set; }
}

有什么办法，我可以添加某种OnDelete事件挂钩，以便每当一个模型是通过 db.Images.Remove（镜像文件）删除; 或什么其他的手段，我可​​以删除相关的文件？

Is there any way I can add some kind of "OnDelete" event hook so that whenever a model is deleted via db.Images.Remove(imageFile); or whatever other means, I can delete the associated file?

推荐答案

您可以覆盖上下文的的SaveChanges 方法挂钩到删除的实体。

You can override the SaveChanges method of your context to hook up to delete entities.

public class GalleryContext : DbContext
{
     public override int SaveChanges()
     {
          var deletedImages = ChangeTracker.Entries()
              .Where(e => e.State == EntityState.Deleted && e.Entity is ImageFile)
              .Select(e => e.Entity).Cast<ImageFile>();

          foreach(var image in deletedImages)
          {
              // delete file here or call a method on image
          }

          return base.SaveChanges();
     }
}

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