5.0 RC1 Many-to-many optional navigation properties

[Atulin]

Right now, it seems that the necessary code to create many-to-many is

class Post
{
  public int Id { get; set; }
  public ICollection<Tag> Tags { get; set; }
}

class Tag
{
  public int Id { get; set; }
  public ICollection<Post> Posts { get; set; }
}

builder.Entity<Post>()
  .HasMany(p => p.Tags)
  .WithMany(t => t.Posts);

but what about optional navigation properties, when I want only Post to have a list of Tags, but not necessarily the Tag to have a list of Posts?

class Post
{
  public int Id { get; set; }
  public ICollection<Tag> Tags { get; set; }
}

class Tag
{
  public int Id { get; set; }
}

builder.Entity<Post>()
  .HasMany(p => p.Tags)
  .WithMany();

That would also be in line with other relationships, where

builder.Entity<Post>()
  .HasOne(p => p.Category)
  .WithMany();

is perfectly valid and doesn't require a Category to contain a collection of Posts.

[ajcvickers]

Related/dupe: #3864

[ajcvickers]

@Atulin This isn't supported for 5.0. I've updated #3864 to indicate that this is the issue tracking unidirectional many-to-many relationships. Please vote for that issue.