public class GradeMap : ClassMap<Grade>
    {
        public GradeMap()
        {
            Id(x => x.GradeId);
            Map(x => x.TaskName).NvarcharWithMaxSize().Not.Nullable();
            Map(x => x.Weight).Not.Nullable().Precision(5).Scale(2);
            Map(x => x.OutOf).Not.Nullable().Precision(5).Scale(2);
            Map(x => x.Mark).Not.Nullable().Precision(5).Scale(2);
            Map(x => x.CourseBackgroundColor).Not.Nullable();
            Map(x => x.CoursePrefix).Not.Nullable();
            References(x => x.Student).Not.Nullable();
            References(x => x.Course);
        }
    }

    public class CourseMap : ClassMap<Course>
    {
        public CourseMap()
        {
     
            Id(x => x.Id).Column("CourseId");
            Map(x => x.Prefix).NvarcharWithMaxSize().Not.Nullable();
            HasMany(x => x.Tasks).Cascade.Delete().Inverse();
            HasMany(x => x.CoursePermissions).Cascade.All().Inverse();
            HasMany(x => x.CourseSharing).Cascade.All().Inverse();
            HasMany(x => x.Grades).Cascade.None().Inverse();
        }
    }

    return session.Query<Grade>().ToList();

    Grade.Course = {Castle.Proxies.CourseProxy}
    Grade.Course.Id = '((new System.Collections.Generic.Mscorlib_CollectionDebugView<OnlGrade>(grades)).Items[0].Course).Id' threw an exception of type 'NHibernate.ObjectNotFoundException'
    Grade.Course.Prefix = above error except .Prefix instead of .Id