CODEWITHSUNDEEP
c#asp.netentity-frameworkef-code-firstcode-first
zahikaram
zahikaram

Reputation: 173

Entity framework - Updating list when updating object

Assume I have a class that is in a independent package and that could be used by Multiple object, for ex:

public class TimeSlot 
{
    [Required]
    public int Id { get; set; }

    [Required]
    public DateTime StartTime { get; set; }

    [Required]
    public DateTime EndTime { get; set; }
}

Not this TimeSlot can be referenced from both the classes below:

public class Business
{
    public int Id { get; set; }

    public virtual IList<TimeSlot> OpeningHours { get; set; }
}

and

public class Delivery
{
    public int Id { get; set; }

    public virtual IList<TimeSlot> DeliveryHours { get; set; }
}

Using Entity Framework code-first, this will result in a TimeSlot table containing both foreign keys to Business and Delivery objects.

Assume I modify a Business object (clear the list of the OpeningHours and add new ones in the code) and update it; once updated, the old TimeSlot records will have the BusinessId foreign key set to NULL instead of being deleted. What's the correct implementation in order to delete those records since they are no longer needed (and preferably without polluting the TimeSlot object)?

Upvotes: 0

Views: 1598

Answers (2)

Gert Arnold
Gert Arnold

Reputation: 109252

With EF it's pretty elaborate to delete child collection elements. When you clear the collection or remove items from it, EF plays safe and does not assume you want to delete the objects, but only want to break the association.

So you have to remove the child items explicitly:

db.TimeSlots.RemoveRange(business.OpeningHours);
db.SaveChanges();

(RemoveRange is EF 6, with earlier versions you have to loop through business.OpeningHours and do db.TimeSlots.Remove()).

Upvotes: 0

Sarbanjeet
Sarbanjeet

Reputation: 253

Change in OnModelCreating in your DbContext class. Add willCascadeOnDelete to true.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

     modelBuilder.Entity<Business>()
      .HasOptional(a => a.OpeningHours)
      .WithOptionalDependent()
      .WillCascadeOnDelete(true);

    base.OnModelCreating(modelBuilder);
}

Upvotes: 2

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