static void Main()
        {
            GroupsDirectory database = new GroupsDirectory();

            // running LINQ query
            var studentsByGroupNameQuery =
                from student in database.StudentsWithGroups
                group student by student.GroupName
                into studentGroup
                orderby studentGroup.Key
                select studentGroup;

            // printing - by invoking the PrintStudentInfoByGroup() method from the StudentsByGroup project
            StudentsByGroupNumber.PrintStudentInfoByGroup(studentsByGroupNameQuery);
        }
        static void Main()
        {
            GroupsDirectory database = new GroupsDirectory();

            // running LINQ query
            var studentsByGroupNameQuery =
                from student in database.StudentsWithGroups
                group student by student.GroupName
                into studentGroup
                orderby studentGroup.Key
                select studentGroup;

            // printing - by invoking the PrintStudentInfoByGroup() method from the StudentsByGroup project
            StudentsByGroupNumber.PrintStudentInfoByGroup(studentsByGroupNameQuery);
        }