private void Add()
        {
            if (string.IsNullOrEmpty(AddData))
            {
                return;
            }

            var parts = AddData.Split(',');

            if (parts.Length != 2)
            {
                return;
            }

            var nameResult = NameConverter.ValidateName(parts[0]);
            var ageResult  = AgeConverter.ValidateAge(parts[1]);

            if (!nameResult || !ageResult)
            {
                MessageBox.Show("Error input");
                return;
            }

            var sytudent = new Student(parts[0], Convert.ToInt32(parts[1]));

            Students.Add(sytudent);
            OnPropertyChanged("Students");
        }