实体框架：更新实体与同类型对象集合的关系

Question

I would like to know if the following is possible with fewer database calls.

I have a model where I need to go back and save other entities of the same type to itself (obviously avoiding circular referencing).

public class OneItemOfTheModel
{
    [Key]
    [Display(Name = "PK Id")]
    public int OneItemOfTheModelPK{ get; set; }

    [Display(Name = "Listing ID")]
    public int ListingID{ get; set; }

    [Display(Name = "Cool Property name")]
    public string CoolProp{ get; set; }

    [Display(Name = "Related Models")]
    public virtual ICollection<OneItemOfTheModel> RelatedModels { get; set; }
    [Display(Name = "Parent Object Thing")]
    public virtual ParentObjectThing ParentObj { get; set; }
 }

Data is imported from rows of a csv file. Initially a "Parent Object Thing" will be created, a new model entity created and linked to that parent and fields populated with the row in the csv:

 ListingID/CoolProp
 1, "whoa"
 2, "awesome"
 3, "data"
 4, "awesome"
 5, "awesome"

The desired result is to end up with the following where entities with the same "Cool Property" are linked in the database:

 PK/ListingID/CoolProp/RelatedModels/ParentObj
 5083,1,"whoa",,53
 5084,2,"awesome",[5086,5087],53
 5085,3,"data",,53
 5086,4,"awesome",[5084,5087],53
 5087,5,"awesome",[5084,5086],53

Currently I am saving entities to the database first and then running another followup method to link individual entities together.

 public void SyncRelatedProperties (int parentObjID, efContext db )
    {
        List<OneItemOfTheModel> myItemList = db.OneItemOfTheModel.Where(b => b.ParentObjID == ParentObjID && b.CoolProp.Length > 0).ToList();
        if (myItemList.Count() > 0)
        {
            foreach( OneItemOfTheModel t in myItemList)
            {
                List<OneItemOfTheModel> tmplist = db.OneItemOfTheModel.Where(b => b.CoolProp == t.CoolProp && b.ListingID != t.ListingID).ToList();
                foreach ( OneItemOfTheModel b in tmplist)
                {
                    t.RelatedModels.Add(b);
                }
            }
        db.SaveChanges();
        }

Obviously this doesn't scale very well when users are importing files with hundreds of lines with tens of related properties to map.

I've played around a bit with "GroupBy" on CoolProp and clearing out the self referencing ListingID but I'm not confident enough with my knowledge of EF to know at what stage I'll be referencing a shallow copy instead of the original entity.

Answer 1

Have you tried just adding all the Entities and calling .SaveChanges()? EF will attempt a Topological Sort on the entities so that they are inserted in an order that is consistent with the foreign key dependencies.