I really need someone to help me to fully understand how to do many-to-many relationship with Entity Framework 4 CTP 5, POCO. I need to understand 3 concepts:
How to config my model to indicates
some tables are many-to-many.
How to properly do insert.
How to properly do update.
Here are my current models:
public class MusicSheet
{
[Key]
public
int ID { get; set; }
public string Title { get; set; }
public string Key { get; set; }
public virtual ICollection<Author> Authors { get; set; }
public virtual ICollection<Tag> Tags { get; set; }
}
public class Author
{
[Key]
public
int ID { get; set; }
public string Name { get; set; }
public string Bio { get; set; }
public virtual ICollection<MusicSheet> MusicSheets { get; set; }
}
public class Tag
{
[Key]
public
int ID { get; set; }
public string TagName { get; set; }
public virtual ICollection<MusicSheet> MusicSheets { get; set; }
}
As you can see, the MusicSheet can have many Authors or Tags, and an Author or Tag can have multiple MusicSheets.
Again, my questions are:
What to do on the
EntityTypeConfiguration to set the
relationship between them as well as
mapping to an table/object that
associates with the many-to-many
relationship.
How to insert a new music sheets
(where it might have multiple
authors or multiple tags).
How to update a music sheet. For
example, I might set TagA,
TagB to MusicSheet1, but later I need to change the tags to TagA
and TagC. It seems like I need
to first check to see if the tags
already exists, if not, insert the
new tag and then associate it with
the music sheet (so that I doesn't
re-insert TagA?). Or this is
something already handled by the
framework?
Thank you very much. I really hope to fully understand it rather than just doing it without fully understand what's going on. Especially on #3.
