Form2.cs

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

namespace MR_Corporation
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
        }

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if ((Keys)e.KeyChar == Keys.Enter)
            {
                string key = textBox1.Text;
                

                if (key.Length != 8)
                {
                    MessageBox.Show( "Error. The number of digits must be 8. Please try again!");
                    return;
                }
                int[] tver=new int[8];
                for(int i=0;i<8;i++)
                    try
                    {
                        tver[i]=int.Parse(key[i].ToString());
                    }
                    catch
                    {
                        MessageBox.Show("Error. All digits must be only numbers. Please try again.");
                        return;
                    }
                string s = "";


                /* The instruction of bites' description*/

                {
                    /*The first bite*/
                    if (tver[0] == 0) s+= 1;
                    if (tver[0] == 1) s+= 0;
                    if (tver[0] == 2) s+= 3;
                    if (tver[0] == 3) s+= 2;
                    if (tver[0] == 4) s+= 5;
                    if (tver[0] == 5) s+= 4;
                    if (tver[0] == 6) s+= 7;
                    if (tver[0] == 7) s+= 6;
                    if (tver[0] == 8) s+= 3;
                    if (tver[0] == 9) s+= 2;

                    /*The second bite*/
                    if (tver[1] == 0) s+= 5;
                    if (tver[1] == 1) s+= 4;
                    if (tver[1] == 2) s+= 3;
                    if (tver[1] == 3) s+= 2;
                    if (tver[1] == 4) s+= 1;
                    if (tver[1] == 5) s+= 0;
                    if (tver[1] == 6) s+= 9;
                    if (tver[1] == 7) s+= 8;
                    if (tver[1] == 8) s+= 7;
                    if (tver[1] == 9) s+= 6;

                    /*The third bite*/
                    if (tver[2] == 0) s+= 9;
                    if (tver[2] == 1) s+= 8;
                    if (tver[2] == 2) s+= 1;
                    if (tver[2] == 3) s+= 0;
                    if (tver[2] == 4) s+= 5;
                    if (tver[2] == 5) s+= 4;
                    if (tver[2] == 6) s+= 7;
                    if (tver[2] == 7) s+= 6;
                    if (tver[2] == 8) s+= 7;
                    if (tver[2] == 9) s+= 6;

                    /*The forth bite*/
                    if (tver[3] == 0) s+= 6;
                    if (tver[3] == 1) s+= 7;
                    if (tver[3] == 2) s+= 8;
                    if (tver[3] == 3) s+= 9;
                    if (tver[3] == 4) s+= 2;
                    if (tver[3] == 5) s+= 3;
                    if (tver[3] == 6) s+= 4;
                    if (tver[3] == 7) s+= 5;
                    if (tver[3] == 8) s+= 8;
                    if (tver[3] == 9) s+= 9;

                    /*The fifth bite*/
                    if (tver[4] == 0) s+= 8;
                    if (tver[4] == 1) s+= 9;
                    if (tver[4] == 2) s+= 0;
                    if (tver[4] == 3) s+= 1;
                    if (tver[4] == 4) s+= 2;
                    if (tver[4] == 5) s+= 3;
                    if (tver[4] == 6) s+= 4;
                    if (tver[4] == 7) s+= 5;
                    if (tver[4] == 8) s+= 0;
                    if (tver[4] == 9) s+= 1;

                    /*The sixth bite*/
                    if (tver[5] == 0) s+= 0;
                    if (tver[5] == 1) s+= 1;
                    if (tver[5] == 2) s+= 8;
                    if (tver[5] == 3) s+= 9;
                    if (tver[5] == 4) s+= 4;
                    if (tver[5] == 5) s+= 5;
                    if (tver[5] == 6) s+= 2;
                    if (tver[5] == 7) s+= 3;
                    if (tver[5] == 8) s+= 2;
                    if (tver[5] == 9) s+= 3;

                    /*The seventh bite*/
                    if (tver[6] == 0) s+= 2;
                    if (tver[6] == 1) s+= 3;
                    if (tver[6] == 2) s+= 0;
                    if (tver[6] == 3) s+= 1;
                    if (tver[6] == 4) s+= 8;
                    if (tver[6] == 5) s+= 9;
                    if (tver[6] == 6) s+= 6;
                    if (tver[6] == 7) s+= 7;
                    if (tver[6] == 8) s+= 0;
                    if (tver[6] == 9) s+= 1;

                    /*The eighth bite*/
                    if (tver[7] == 0) s+= 6 ;
                    if (tver[7] == 1) s+= 7 ;
                    if (tver[7] == 2) s+= 4 ;
                    if (tver[7] == 3) s+= 5 ;
                    if (tver[7] == 4) s+= 0 ;
                    if (tver[7] == 5) s+= 1 ;
                    if (tver[7] == 6) s+= 8 ;
                    if (tver[7] == 7) s+= 9 ;
                    if (tver[7] == 8) s+= 8 ;
                    if (tver[7] == 9) s+= 9 ;
                }

                textBox2.Text = s;

            }
        }
    }
}