many-to-many-relation with only one single table on both ends

Hello,

I have problems to create a many-to-many-relation with only one single table on both ends.

For this reason I have created to tables:
Word:
Id        Integer
Text        Text
Links        Collection<Word>
ReverseLinks    Collection<Word>

WordWord:
WordId        Integer
WordReverseId    Integer

Each word can have none, one or serval link(s) to other words. Inversely, every word can be linked by none, one or serveral words.
I want be able to access these links like (i.e. by means of a ThroughAssociation):
Word word1 = new Word();
word1.Text = "1st word";
Word word2 = new Word();
word2.Text = "2nd word";
word1.Links.add(word2);
//word1.Links[0].Text == "2nd word";
//word2.ReverseLinks[0].Text == "1st word";

So far, I have only found a workaround:
1st: Definition of both domain classes:
    public class Word : Entity<int>
    {
        private string _Text;

        public readonly EntityCollection<WordToWord> _WordLinks = new EntityCollection<WordToWord>();
        public readonly EntityCollection<WordToWord> _WordLinksReverse = new EntityCollection<WordToWord>();

        public string Text
        {
            get { return _Text; }
            set { this.Set(ref _Text, value); }
        }
        public EntityCollection<WordToWord> WordLinks
        {
            get { return Get(_WordLinks); }
        }
        public EntityCollection<WordToWord> WordLinksReverse
        {
            get { return Get(_WordLinksReverse); }
        }
    }

    public class WordToWord : Entity<int>
    {
        private int _WordId;
        private int _LinkedToWordId;

        [ReverseAssociation("WordLinks")]
        public readonly EntityHolder<Word> _Word = new EntityHolder<Word>();
        [ReverseAssociation("WordLinksReverse")]
        public readonly EntityHolder<Word> _LinkedToWord = new EntityHolder<Word>();

        public Word Word
        {
            get { return Get(_Word); }
            set { Set(_Word, value); }
        }
        public Word LinkedToWord
        {
            get { return Get(_LinkedToWord); }
            set { Set(_LinkedToWord, value); }
        }
    }

2nd: Application of these classes:
    Word word1 = new Word();
    word1.Text = "1st word";

        Word word2 = new Word();
        word2.Text = "2nd word";

        WordToWord wordToWord = new WordToWord();
        wordToWord.Word = word1;
        wordToWord.LinkedToWord = word2;
        word1.WordLinks.Add(wordToWord);

        workUnit.Add(word1);
        workUnit.Add(word2);
        workUnit.SaveChanges();



Is there any possiblity to realize this with ThroughAssociations?
Thanks for your answer,
Henning

Hi Henning,

Yes - you can define a couple of ThroughAssociations on the Word class for this. If you are using the Designer to generate your model then I would add them in to a partial, otherwise you can add them directly in to your existing class definition .

e.g.

private readonly ThroughAssociation<WordToWord, Word> _linkedWords;

private readonly ThroughAssocation<WordToWord, Word> _reverseLinkedWords;

public Word()

{

  _linkedWords = new ThroughAssociation<WordToWord, Word>(_WordLinks);

  _reverseLinkedWords = new ThroughAssociation<WordToWord, Word(_WordLinksReverse);

}

public ThroughAssociation<WordToWord, Word> LinkedWords

{

  get { return _linkedWords; }

}

public ThroughAssociation<WordToWord, Word> ReverseLinkedWords

{

  get { return _reverseLinkedWords; }

}

Note that you will want to eager load those two collections to have the ThroughAssociations correctly initialized when the constructor fires.

Jeremy