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One to many recursive relationship with Code First


One to many recursive relationship with Code First

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One to many recursive relationship with Code First
Tag : entity-framework , By : afarouk
Date : November 23 2020, 01:01 AM

fixed the issue. Will look into that further Cause of the exception
The exception is caused by a Select or SelectMany on a null collection, in your case the result of
b => b.Children
selector(node)
IEnumerable<Branch> anonymousMethod(Branch b)
{
    return b.Children;
}
public virtual ICollection<Branch> Children { get; set; }
public static IEnumerable<T> Flatten<T>(this T node, Func<T,IEnumerable<T>> selector)
{
    return new[] { node }
        .Concat(selector(node).SelectMany(x => Flatten(x, selector)));
}    

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How to setup relationship in cakephp for a one-to-one recursive relationship?


Tag : cakephp , By : Lucas Thompson
Date : March 29 2020, 07:55 AM
help you fix your problem I am new to cakePHP and I am trying to figure out how to create the following relationship: , you can define following association:
class Employee extrnds AppModel {
var $belongsTo = array(
            'Parent' => array('className' => 'Employee',
                                'foreignKey' => 'manager_id',
                                'conditions' => '',
                                'fields' => '',
                                'order' => ''
            )
    );
}
$this->Employee->Parent->find('list');

Self-referencing many-to-many recursive relationship code first Entity Framework


Tag : chash , By : Kenny
Date : March 29 2020, 07:55 AM
like below fixes the issue By convention, Code First will take uni-directional associations as one to many. Therefore you need to use fluent API to let Code First know that you want to have a many to many self referencing association:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Member>().HasMany(m => m.Friends).WithMany().Map(m =>
        {
            m.MapLeftKey("MemberId");
            m.MapRightKey("FriendId");
            m.ToTable("MembersFriends");
        }
    );
}

what is the use of recursive relationship and a relationship to an undefined model in Django?


Tag : python , By : Sharad
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further You can use it to create links to other objects of this Model.
For example if you have many members in a website and each has an inviter (also of Member type) you can do the following:
class Member(Model):
    inviter = models.ForeignKey(
        'self',
        related_name="invited_set"
    )
Member.objects.get(id__exact=5).inviter
Member.objects.get(id__exact=5).invited_set

EF5 Code First: Force many to many recursive relationship


Tag : chash , By : walshtp
Date : March 29 2020, 07:55 AM
will be helpful for those in need You can specify with Fluent API that the relationship is of type many-to-many (and not a one-to-many relationship which EF assumes by default):
public class MyContext : DbContext
{
    //...
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Entry>()
            .HasMany(e => e.RelatedEntries)
            .WithMany()
            .Map(m =>
            {
                m.MapLeftKey("Entry_Id");
                m.MapRightKey("Related_Entry_Id");
                m.ToTable("EntryRelations");
            });
    }
}

Django Reverse relationship with Recursive M2M Relationship


Tag : django , By : Sid
Date : March 29 2020, 07:55 AM
will help you This seems to be a duplicate of How to make recursive ManyToManyField relationships that have extra fields symmetrical in Django? but i cant mark them
Basicly this is not possible in django as you have to define symmetrical=False. You have the option to add a second m2m field for the other way around. The other thread has some good reads about that
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