Mamy to Many Entity

public class Member
{
    public int MemberID { get; set; }
 
    public string FirstName { get; set; }
    public string LastName { get; set; }
 
    public virtual ICollection<MemberComment> MemberComments { get; set; }
}
 
public class Comment
{
    public int CommentID { get; set; }
    public string Message { get; set; }
 
    public virtual ICollection<MemberComment> MemberComments { get; set; }
}
 
public class MemberComment
{
    [Key, Column(Order = 0)]
    public int MemberID { get; set; }
    [Key, Column(Order = 1)]
    public int CommentID { get; set; }
 
    public virtual Member Member { get; set; }
    public virtual Comment Comment { get; set; }
 
    public int Something { get; set; }
    public string SomethingElse { get; set; }
}

var commentsOfMembers = context.Members
    .Where(m => m.LastName == "Smith")
    .SelectMany(m => m.MemberComments.Select(mc => mc.Comment))
    .ToList();

var commentsOfMembers = context.MemberComments
    .Where(mc => mc.Member.LastName == "Smith")
    .Select(mc => mc.Comment)
    .ToList();

var membersWithComments = context.Members
    .Where(m => m.LastName == "Smith")
    .Select(m => new
    {
        Member = m,
        Comments = m.MemberComments.Select(mc => mc.Comment)
    })
    .ToList();

var commentsOfMember = context.MemberComments
    .Where(mc => mc.MemberId == 1)
    .Select(mc => mc.Comment)
    .ToList();

var filteredCommentsOfMember = context.MemberComments
    .Where(mc => mc.MemberId == 1 && mc.Something == 99)
    .Select(mc => mc.Comment)
    .ToList();

var member1 = new Member { FirstName = "Pete" };
var comment1 = new Comment { Message = "Good morning!" };
var comment2 = new Comment { Message = "Good evening!" };
var memberComment1 = new MemberComment { Member = member1, Comment = comment1,
                                         Something = 101 };
var memberComment2 = new MemberComment { Member = member1, Comment = comment2,
                                         Something = 102 };
 
context.MemberComments.Add(memberComment1); // will also add member1 and comment1
context.MemberComments.Add(memberComment2); // will also add comment2
 
context.SaveChanges();

var member1 = context.Members.Where(m => m.FirstName == "Pete")
    .SingleOrDefault();
if (member1 != null)
{
    var comment3 = new Comment { Message = "Good night!" };
    var memberComment3 = new MemberComment { Member = member1,
                                             Comment = comment3,
                                             Something = 103 };
 
    context.MemberComments.Add(memberComment3); // will also add comment3
    context.SaveChanges();
}

var comment2 = context.Comments.Where(c => c.Message == "Good evening!")
    .SingleOrDefault();
if (comment2 != null)
{
    var member2 = new Member { FirstName = "Paul" };
    var memberComment4 = new MemberComment { Member = member2,
                                             Comment = comment2,
                                             Something = 201 };
 
    context.MemberComments.Add(memberComment4);
    context.SaveChanges();
}

var member2 = context.Members.Where(m => m.FirstName == "Paul")
    .SingleOrDefault();
var comment3 = context.Comments.Where(c => c.Message == "Good night!")
    .SingleOrDefault();
if (member2 != null && comment3 != null)
{
    var memberComment5 = new MemberComment { Member = member2,
                                             Comment = comment3,
                                             Something = 202 };
 
    context.MemberComments.Add(memberComment5);
    context.SaveChanges();
}

var memberComment5 = context.MemberComments
    .Where(mc => mc.Member.FirstName == "Paul"
        && mc.Comment.Message == "Good night!")
    .SingleOrDefault();
if (memberComment5 != null)
{
    context.MemberComments.Remove(memberComment5);
    context.SaveChanges();
}

var member1 = context.Members.Where(m => m.FirstName == "Pete")
    .SingleOrDefault();
if (member1 != null)
{
    context.Members.Remove(member1);
    context.SaveChanges();
}