RegistrationForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Student_Registration_Form
{
    public partial class RegistrationForm : Form
    {
        // Variables and methods for making the borderless form movable
        public const int WM_NCLBUTTONDOWN = 0xA1;
        public const int HT_CAPTION = 0x2;
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
        [System.Runtime.InteropServices.DllImport("user32.dll")]
        public static extern bool ReleaseCapture();

        // Variables for the register form
        string first_name, middle_name, last_name;
        int day, month, year;
        bool isMale;

        // Constructor
        public RegistrationForm()
        {
            InitializeComponent();
        }

        // Event Method when the Form Load
        private void RegistrationForm_Load(object sender, EventArgs e)
        {
            setDefaultValue();
            populateDay();
            populateMonth();
            populateYear();
        }

        // Event method that makes the borderless form movable
        private void Form1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                ReleaseCapture();
                SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
            }
        }

        // Closes the Application when clicking the X
        private void close_button_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        // When clicking the register button
        private void register_button_Click(object sender, EventArgs e)
        {
            try
            {
                fetchData();
                new OutputForm(outputText()).ShowDialog(this);
            } 
            catch (Exception ex)
            {
                MessageBox.Show("Please input all the fields", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        // Method for the Default value of the Combobox
        public void setDefaultValue()
        {
            // Default Value for Day Combobox
            DayComboBox.Items.Insert(0, "-Day-");
            DayComboBox.SelectedIndex = 0;

            // Default Value for Month Combobox
            MonthComboBox.Items.Insert(0, "-Month-");
            MonthComboBox.SelectedIndex = 0;

            // Default Value for Year Combobox
            YearComboBox.Items.Insert(0, "-Year-");
            YearComboBox.SelectedIndex = 0;
        }

        // Method that populates the Day Combobox
        public void populateDay()
        {
            for (int x = 1; x <= 31; x++) DayComboBox.Items.Add(x);
        }

        // Method that populates the Month Combobox
        public void populateMonth()
        {
            for (int x = 1; x <= 12; x++) MonthComboBox.Items.Add(x);
        }

        // Method that populates the Year Combobox
        public void populateYear()
        {
            for (int x = 1900; x <= DateTime.Now.Year; x++) YearComboBox.Items.Add(x);
        }

        // Method of fetching the data that is written by the user
        public void fetchData()
        {
            // Fetching the name
            first_name = FirstNameTextbox.Text;
            middle_name = MiddleNameTextbox.Text;
            last_name = LastNameTextbox.Text;

            // Call the checker method 
            checkNull(first_name);
            checkNull(middle_name);
            checkNull(last_name);

            // Fetching the date of birth
            day = Int32.Parse(DayComboBox.Text);
            month = Int32.Parse(MonthComboBox.Text);
            year = Int32.Parse(YearComboBox.Text);

            // Throws an exception if either of them are not selected
            if (!MaleRadioButton.Checked && !FemaleRadioButton.Checked) throw new Exception();

            // set isMale to true when selected else false
            if (MaleRadioButton.Checked) isMale = true; else isMale = false;
        }

        // Check if the field is null or empty then throws an exception
        public void checkNull(string data)
        {
            if (data == null || data.Trim() == "") throw new Exception();
        }

        // Method that returns the output of the program
        public string outputText()
        {
            return string.Format(
                "Student name:\n{0} {1} {2}\n\n" + "Gender:\n{3}\n\n" + "Date of birth:\n{4}/{5}/{6}\n",
                first_name, middle_name, last_name, (isMale ? "Male" : "Female"),day, month, year);
        }
    }
}