Removing child entity not deleting in database entity framework

Question

I have two entities "YogaSpace" and "YogaSpaceImage" I'm deleting an image and trying to get the row removed, instead it just nulls out the reference to the YogaSpace entity.

Here are my entities.

public class YogaSpace
{
    public int YogaSpaceId { get; set; }
    public virtual ICollection<YogaSpaceImage> Images { get; set; }
}

public class YogaSpaceImage
{
    public int YogaSpaceImageId { get; set; }
    public byte[] Image { get; set; }
    public byte[] ImageThumbnail { get; set; }
    public string ContentType { get; set; }
    public int Ordering { get; set; }
}

Here is the method that deleted one image from the db.

[HttpPost]
    public ActionResult RemoveImage(string id, string imageId)
    {
        YogaSpace yogaSpace = yogaSpaceRepository.Find(Convert.ToInt16(id));
        YogaSpaceImage image = yogaSpace.Images.FirstOrDefault(si => si.YogaSpaceImageId == Convert.ToInt16(imageId));
        yogaSpace.Images.Remove(image);

        yogaSpaceRepository.InsertOrUpdate(yogaSpace);
        yogaSpaceRepository.Save();

        return Json("removed");
    }

here is what's inside my repo to insertorupdate()

public void InsertOrUpdate(YogaSpace yogaSpace)
    {
        if (yogaSpace.YogaSpaceId == default(int))
        {
            context.Entry(yogaSpace).State = System.Data.Entity.EntityState.Added;
        }
        else
        {
            context.Entry(yogaSpace).State = System.Data.Entity.EntityState.Modified;
        }
    }

and here is the result. you can see the row doesn't get deleted, null gets put into the reference column. I don't have a repo for YogaSpaceImage entity, only YogaSpace so trying to use it so I don't have to create another repo. enter image description here

Michal Ciechan · Answer 1 · 2015-03-21T00:59:35.307

0

You need to mark the entity as deleted.

yogaSpace.Images.Remove(image);
context.YogaSpaceImages.Remove(image)

your other option is to mark you mapping with .WillCascadeOnDelete()

E.g.

protected override void OnModelCreating(DbModelBuilder mb)
{

    mb.Entity<YogaSpace>().HasMany(p => p.Images )
        .WithRequired()
        .HasForeignKey(c => c.YogaSpaceImageId)
        .WillCascadeOnDelete();

}

The other option is to have a ForeignKey on the YogaSpaceImage back to the YogaSpace (if it is a mapping of 1 YogaSpace - 0-many Image) and mark the YogaSpaceImage.YogaSpace foreign key required. Therefore whenever EF tried to remove the foreign key, it will automatically delete the Image.

public class YogaSpaceImage
{
    public int YogaSpaceImageId { get; set; }        
    public byte[] Image { get; set; }
    public byte[] ImageThumbnail { get; set; }
    public string ContentType { get; set; }
    public int Ordering { get; set; }

    public int YogaSpaceId { get; set; }
    [Required] <-- This will delete the image, if removed from parent
    public virtual YogaSpace YogaSpace { get; set; }
}

edited Mar 21 '15 at 00:59

answered Mar 21 '15 at 00:29

Michal Ciechan

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is there any way to use .willcascadeondelete in the RemoveImage() code? or a way to use data annotations? isn't this method above for fluent api? – chuckd Mar 21 '15 at 00:45
Yes, see the first part, you can manually remove that image from the `YogaSpaceImages` `DbSet`. This will delete the row on SaveChanges() – Michal Ciechan Mar 21 '15 at 00:53
I tried adding this onModelCreating code but now I get a error when starting up that relates to the multiplicity of yogaspace images – chuckd Mar 21 '15 at 00:53
no this is a one to many relationship. Is this syntax correct for a one-to-many rel? – chuckd Mar 21 '15 at 00:55
If thats the case you will have to go to the database, make sure that the image is not referenced by any other YogaSpace, and then remove it. – Michal Ciechan Mar 21 '15 at 00:55
Or remove it and catch the foreign key constraint exception. – Michal Ciechan Mar 21 '15 at 00:56
if you want it to be 1 to many then edit your `YogaSpaceImage` by adding the `[Required]YogaSpaceId` and `virtual YogaSpace` – Michal Ciechan Mar 21 '15 at 00:57
When you mark it the navigation property as required, EF will automatically cascade the delete, as an `Image` is required to have a `YogaSpace`, if EF sees that it would cause it to not have one, it will delete it. – Michal Ciechan Mar 21 '15 at 00:59
let me give this a try. hold one sec – chuckd Mar 21 '15 at 01:03
no, this doesn't work. Are you sure you have the syntax correct for a one-to-many rel? – chuckd Mar 21 '15 at 01:06
I'm looking here http://www.entityframeworktutorial.net/code-first/configure-one-to-many-relationship-in-code-first.aspx – chuckd Mar 21 '15 at 01:07
did you add the required attribute? – Michal Ciechan Mar 21 '15 at 01:17
yes I tried this. It doesn't work. I'm not sure I've seen a required attribute on a virtual call before on entities, can you provide any links or tutorials that show this? – chuckd Mar 21 '15 at 01:42
try putting it on YogaSpaceId – Michal Ciechan Mar 21 '15 at 01:53
or making the navigation property non virtual – Michal Ciechan Mar 21 '15 at 01:57
im downloading SSMS as i reformatted my pc recently, will take hours, so going sleep, will check back in the morning – Michal Ciechan Mar 21 '15 at 01:57
http://stackoverflow.com/questions/5471374/how-do-you-ensure-cascade-delete-is-enabled-on-a-table-relationship-in-ef-code-f – Michal Ciechan Mar 21 '15 at 01:57
not sure if this makes a difference but I'm not deleting the yogaspace and all child entities, I'm just deleting the image (child entity) – chuckd Mar 21 '15 at 02:00
by deleting the image, you mean removing it from YogaSpace – Michal Ciechan Mar 21 '15 at 02:00
yes, but actually it would be deleting it from yogaspaceimage. – chuckd Mar 21 '15 at 08:51

Removing child entity not deleting in database entity framework

1 Answers1