c# - Struggling with EF CodeFirst 1 to Many relationship -

i able tag movie category.

public class movie {    public virtual observablecollection<category> categories { get; set; }     public void addcategory(string name)    {        using (var dbcontext = new mydbcontext())        {            var category = dbcontext.categories.singleordefault(x => x.name == name) ?? new category(name, dbcontext);            categories.add(category);            dbcontext.savechanges();        }    } }  public class category() {     public category(string name, dbcontext dbcontext)     {         name = name;         dbcontext.categories.add(this);         dbcontext.savechanges();     } } 

if category not exist, created , dbcontext.categories.add(this) called inside category c'tor.

there no errors, new category not saved movie.categories.

i guessing because movie class belongs different context? unsure how structure this.

edit: if using database first approach, result movie_categories table has movie_id , category_id. why difficult?

i think want many-to-many relationship: 1 movie can have many categories , 1 category can belong many movies.

so category class needs public virtual icollection<movie> movies {get; set; } property.

your movie class this:

public class movie {    public virtual icollection<category> categories { get; set; }     public void addcategory(string name)    {        using (var dbcontext = new mydbcontext())        {            // movie object dbcontext attached            var movie = dbcontext.movies.singleordefault(m => m.name == name); // or match movie id instead of name            var category = dbcontext.categories.singleordefault(x => x.name == name) ?? new category(name);            movie.categories.add(category);             dbcontext.savechanges();        }    } } 

and category class:

public class category {   public virtual icollection<movie>() movies { get; set; }   public string name { get; set;}    public category(string name)   {     name = name;   }  }