private void button1_Click(object sender, EventArgs e)
        {
            string error_caption = "Error";

            if (string.IsNullOrEmpty(EmployeeName.Text))
            {
                var emp_error = MessageBox.Show("Employee Name cannot be left empty", error_caption, MessageBoxButtons.OK);
                EmployeeName.Focus();
            }

            else if (!BirthDate.MaskCompleted || !BirthDate.MaskFull)
            {
                var emp_error = MessageBox.Show("Birth date is not filled or not finished yet", error_caption, MessageBoxButtons.OK);
                BirthDate.Focus();
            }

            else if (string.IsNullOrEmpty(Address.Text))
            {
                var emp_error = MessageBox.Show("Address is cannot be left empty", error_caption, MessageBoxButtons.OK);
                Address.Focus();
            }

            else if (City.SelectedIndex < 0)
            {
                var emp_error = MessageBox.Show("Please choose a city", error_caption, MessageBoxButtons.OK);
                City.Focus();
            }

            else if (Country.SelectedIndex < 0)
            {
                var emp_error = MessageBox.Show("Please choose your nation", error_caption, MessageBoxButtons.OK);
                Country.Focus();
            }

            else if (Qualification.SelectedIndex < 0)
            {
                var emp_error = MessageBox.Show("Please choose your highest qualification", error_caption, MessageBoxButtons.OK);
                Qualification.Focus();
            }


            else if (!Phone.MaskCompleted)
            {
                var emp_error = MessageBox.Show("Please enter your phone number", error_caption, MessageBoxButtons.OK);
                Phone.Focus();
            }

            else if (string.IsNullOrEmpty(Email.Text))
            {
                var emp_error = MessageBox.Show("Please enter your Email", error_caption, MessageBoxButtons.OK);
                Email.Focus();
            }

            else if (JoinDate.Text.Length == 0)
            {
                var emp_error = MessageBox.Show("When did you join this company?", error_caption, MessageBoxButtons.OK);
                JoinDate.Focus();
            }

            else
            {
                string message = "Employee Name: " + this.EmployeeName.Text
                                 + "\nDate of birth: " + this.BirthDate.Text
                                 + "\nAddress: " + this.Address.Text
                                 + "\nCity: " + this.City.Text
                                 + "\nCountry: " + this.Country.Text
                                 + "\nQualification: " + this.Qualification.Text
                                 + "\nPhone: " + this.Phone.Text
                                 + "\nEmail: " + this.Email.Text
                                 + "\nDate of joining: " + this.JoinDate.Text;
                string caption = "Information detail";
                var    result  = MessageBox.Show(message, caption, MessageBoxButtons.OK);
            }
        }