插入重复值的实体框架6

I have following two entities:

我有以下两个实体:

public class Artist
{
    [Key]
    public string ArtistId { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Genre> Genres { get; set; }
}

public class Genre
{
    [Key]
    public int GenreId { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Artist> Artist { get; set; }
}
pu