private void button1_Click(object sender, EventArgs e)
        {
            string         studentselected = this.comboBox1.GetItemText(this.comboBox1.SelectedItem);
            string         gradetext       = this.comboBox2.GetItemText(this.comboBox2.SelectedItem);
            int            grade           = Int32.Parse(gradetext);
            int            studentid       = 0;
            int            teacherid       = 0;
            List <Teacher> teacherlist     = duombaze.GetTeacher();

            foreach (Teacher teacher in teacherlist)
            {
                if (MainWindow.LoggedInUser.GetFullName() == teacher.Name + " " + teacher.Surname)
                {
                    teacherid = teacher.Id;
                }
            }



            int            lessonid    = 0;
            List <Student> studentlist = duombaze.GetStudent();

            foreach (Student student in studentlist)
            {
                if (studentselected == student.Name + " " + student.Surname)
                {
                    studentid = student.Id;
                }
            }
            List <Lesson> lessonlist = duombaze.Getlesson();

            foreach (Lesson lesson in lessonlist)
            {
                if (lesson.Teacherid == teacherid)
                {
                    lessonid = lesson.Id;
                }
            }

            duombaze.AddNewGrade(grade, studentid, teacherid, lessonid);
            MessageBox.Show("Pazymis sekmingai pridetas");
            this.Close();
        }