Question

i am having a four models.. User,post,tag,comment.. the relationship i want to have with EF code first is

1) 1 user can have many posts, can create many tags, can have many comments
2) 1 post can have 1 user, many comments, and can have many tags
3) 1 tag can have 1 user, many post
4) 1 comment can have 1 user, 1 post

through google, i have come this far …but i am sure its not right …please help..

Updated Mapping

 modelBuilder.Entity<User>().HasMany(p => p.Posts).WithRequired(u => u.Users);
        modelBuilder.Entity<User>().HasMany(t => t.Tags).WithRequired(u => u.Users);
        modelBuilder.Entity<User>().HasMany(c => c.Comments).WithRequired(u => u.Users);

        modelBuilder.Entity<Post>().HasRequired(u => u.Users);
        modelBuilder.Entity<Post>().HasMany(t => t.Tags).WithMany(p => p.Posts);
        modelBuilder.Entity<Post>().HasMany(c => c.Comments);

        modelBuilder.Entity<Comment>().HasRequired(u => u.Users);
        modelBuilder.Entity<Comment>().HasRequired(p => p.Posts);

        modelBuilder.Entity<Tag>().HasRequired(u => u.Users);
        modelBuilder.Entity<Tag>().HasMany(p => p.Posts).WithMany(t => t.Tags);

please help.

Answer 1

If one User can have many Posts and Post can have single User your entities and mappings must be prepared for that.

public class User 
{
    ...
    public virtual ICollection<Post> Posts { get; set; }
}

public class Post
{
    ...
    public virtual User { get; set;}
    public virtual ICollection<Tag> { get; set; }
}

public class Tag
{
    ...
    public virtual ICollection<Post> Posts { get; set; }
}

If you define your entities correctly it should make correct mapping for you with default conventions. If you still to map it with fluent API you must use:

modelBuilder.Entity<User>().HasMany(u => u.Posts).WithRequired(p => p.User);

Which means one user can have many posts and post must have single user. That is 1-N mapping. For tag and post you need M-N mapping:

modelBuilder.Entity<Tag>().HasMany(t => t.Posts).WithMany(p => p.Tags);

Which means one tag can have many posts and post can have many tags.

You will map other relations in the same way.