CODEWITHSUNDEEP
entity-frameworkef-code-first
Diver Dan
Diver Dan

Reputation: 9963

Deleting an entity record in a many to many relationship with EF6

I am doing something wrong when trying to remove a related record. I have a Customer model and a CustomerGroup model. A customer can belong to multiple customergroups.

I want to be able to add and remove a customer from a customergroup. Adding is the easy part, when I try to remove a customer from a customergroup the entire record is deleted from the customergroup table

To make things easy to understand here is my code.

 [Table("CustomerGroups")]
public class CustomerGroupModel
{
    [Key]
    [DataMember]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid CustomerGroupId { get; set; }

    [DataMember]
    public Guid BusinessId { get; set; }
    public virtual Business Business { get; set; }

    [DataMember]
    [Display(Name = "Group Name")]
    public string GroupName { get; set; }

     [ScriptIgnore]
    public virtual List<Customer> CustomersInGroup { get; set; }
}

My Customer model

   [Table("Customers")]
[DataContract]
public class Customer
{

    [DataMember]
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public Guid Id { get; set; }

    [DataMember(IsRequired = true)]
    [Required(ErrorMessage = "First Name is required")]
    [Display(Name = "First Name")]
    public string FirstName { get; set; }

    [DataMember(IsRequired = true)]
    [Required(ErrorMessage = "Last Name is required")]
    [Display(Name = "Last Name")]
    public string LastName { get; set; }


    [DataMember]
    public string FullName
    {
        get { return string.Format("{0} {1}", FirstName, LastName); }
    }


    [DataMember]
    [Display(Name = "Groups")]
    //change this as ICollection failed with restsharp to bindICollection<CustomerGroupModel> SelectedGroups { get; set; }
    public virtual List<CustomerGroupModel> SelectedGroups { get; set; }


}

My FluentApi

            modelBuilder.Entity<Customer>()
            .HasMany(x => x.SelectedGroups)
            .WithMany(x => x.CustomersInGroup).Map(
                m =>
                {
                    m.MapLeftKey("CustomerId");
                    m.MapRightKey("CustomerGroupId");
                    m.ToTable("CustomersInGroups");
                });

As you can see I generate a table called CustomersInGroups.

When I try to update customer groups I want to delete all existing records then reinsert the newly selected ones (unless there is a better way of doing this)

            using (var context = new MyContext())
            {
                var contextCustomer = context.Customers
                    .Include("SelectedGroups")
                    .SingleOrDefault(a => a.Id==customer.Customer.Id); 

                contextCustomer.SelectedGroups.ToList()
                        .ForEach(r => context.CustomerGroups.Remove(r));
                context.SaveChanges();

             }

When I execute this all records from the table CustomerGroups are deleted. How do I only delete the related records from the customersingroups table?

Any advice would be really appreciated

Upvotes: 1

Views: 887

Answers (1)

M&#225;rk Gergely Dolinka
M&#225;rk Gergely Dolinka

Reputation: 1460

The reason the CustomerGroup records are deleted is that you remove them from the context that is translated as removing them entirely from the database. To remove only the relationships between the CustomerGroup instances related to the selected customer you have to assign an empty list to the SelectedGroups property:

contextCustomer.SelectedGroups = new List<CustomerGroups>();
context.SaveChanges();

Upvotes: 1

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