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"); }