Question

Have three classes User, Group and Field. Many to many relationship on User / Group and a many to many relationship on Group Field. The User / Group relationship is pretty simple as a User is simply a member of the Group or not. The Group / Field relationship is more complex as there is an Authority property on that relationship.

In the ctor I pass HashSets of the relationships so there is one master.

Finally to the question. How can I filter to the Group FieldAuthority better? See ?? in code below.

    public class Group : Object
    {
        private HashSet<UserGroup> usersGroups;
        private HashSet<GroupFieldAuthority> groupsFieldsAuthority;

        public Int16 ID { get; private set; }
        public string Name { get; set; }

        public List<User> Users
        { get { return usersGroups.Where(x => x.Group == this).Select(x => x.User).OrderBy(x => x.UserID).ToList(); } }
        public List<FieldAuthority> FieldsAuthority
        {     
            get
            {
                // Can this be done more directly??
                List<FieldAuthority> fieldsAuthority = new List<FieldAuthority>();
                foreach (GroupFieldAuthority gfa in groupsFieldsAuthority.Where(x => x.Group == this).OrderBy(x => x.Group.Name))
                {
                    fieldsAuthority.Add(new FieldAuthority(gfa.FieldDef, gfa.Authority));
                }
                return fieldsAuthority;
            }
        }
        public override bool Equals(Object obj)
        {
            //Check for null and compare run-time types.
            if (obj == null || GetType() != obj.GetType()) return false;
            Group fd = (Group)obj;
            return (ID == fd.ID);
        }
        public override int GetHashCode() { return (int)ID; }
        public Group(Int16 id, string name, HashSet<UserGroup> UsersGroups, HashSet<GroupFieldAuthority> GroupsFieldsAuthority)
        { ID = id; Name = name; usersGroups = UsersGroups;  groupsFieldsAuthority = GroupsFieldsAuthority; }
    }
    public class GroupFieldAuthority : Object
    {
        public Group Group { get; private set; }
        public FieldDef FieldDef { get; private set; }
        public enumAuthRORWMADeny Authority { get; private set; }
        public override bool Equals(Object obj)
        {
            //Check for null and compare run-time types.
            if (obj == null || GetType() != obj.GetType()) return false;
            GroupFieldAuthority item = (GroupFieldAuthority)obj;
            return (Group.ID == item.Group.ID);
        }
        public override int GetHashCode() { return (int)Group.ID ^ (int)FieldDef.ID; }
        public GroupFieldAuthority(Group group, FieldDef fieldDef, enumAuthRORWMADeny authority)
        { Group = group; FieldDef = fieldDef; Authority = authority; }
    }
    public class FieldAuthority : Object
    {   // used for FieldDef and Document
        public FieldDef FieldDef { get; private set; }
        public enumAuthRORWMADeny Authority { get; private set; }
        public override bool Equals(Object obj)
        {
            //Check for null and compare run-time types.
            if (obj == null || GetType() != obj.GetType()) return false;
            FieldAuthority item = (FieldAuthority)obj;
            return (FieldDef.ID == item.FieldDef.ID);
        }
        public override int GetHashCode() { return (int)FieldDef.ID; }
        public FieldAuthority(FieldDef fieldDef, enumAuthRORWMADeny authority)  
        { FieldDef = fieldDef; Authority = authority; }
    }

Answer 1

Is that what do you want?

return groupsFieldsAuthority
         .Where(x => x.Group == this)
         .OrderBy(x => x.Group.Name)
         .Select(x => new FieldAuthority(x.FieldDef, x.Authority))
         .ToList();