private void fillDisciplineTextBox(StudentGradesWindow gradesWindow, int i)
        {
            string discipline         = "Discipline" + i;
            var    disciplineTextBloc = (TextBlock)gradesWindow.FindName(discipline);
            string gradeDiscipline    = StudentGrades[i].Discipline;

            isTextBoxNull(gradeDiscipline, disciplineTextBloc);
        }
        private void fillFormOfControlTextBox(StudentGradesWindow gradesWindow, int i)
        {
            string formOfControl        = "FormOfControl" + i;
            var    formOfControlTextBox = (TextBlock)gradesWindow.FindName(formOfControl);
            string gradeFormOfControl   = StudentGrades[i].FormOfControl.ToString();

            isTextBoxNull(gradeFormOfControl, formOfControlTextBox);
        }
        private void fillGradeTextBox(StudentGradesWindow gradesWindow, int i)
        {
            string grade           = "Grade" + i;
            var    gradeTextBox    = (TextBlock)gradesWindow.FindName(grade);
            string disciplineGrade = StudentGrades[i].Grade.ToString();

            isTextBoxNull(disciplineGrade, gradeTextBox);
        }
        private void fillLastChangedControlTextBox(StudentGradesWindow gradesWindow, int i)
        {
            string lastChanged        = "LastChanged" + i;
            var    lastChangedTextBox = (TextBlock)gradesWindow.FindName(lastChanged);
            string gradeLastChanged   = StudentGrades[i].LastChanged.ToString();

            isTextBoxNull(gradeLastChanged, lastChangedTextBox);
        }