MainForm

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;
using System.Text.RegularExpressions;

namespace WindowsFormsApplication4
{
    public partial class Furnish : Form
    {
        List<Item> items = new List<Item>();

        public void match(Regex Reg, TextBox box, Label lab)
        {
            if (Reg.IsMatch(box.Text))
            {
                lab.ForeColor = Color.LimeGreen;
                lab.Text = "Complete";
            }
            else
            {
                lab.ForeColor = Color.Red;
                lab.Text = "*Required";
            }
        }

        public void allClear()
        {
            nameText.Clear();
            priceText.Clear();
            urlText.Clear();
            nameLabel.Text = "";
            priceLabel.Text = "";
            urlLabel.Text = "";
        }

        public Furnish()
        {
            InitializeComponent();
        }

        private void addButton_Click(object sender, EventArgs e)
        {
            Regex url = new Regex(@"^[a-zA-Z0-9\-\.]+\.(com|org|net|ca|mil|edu|COM|ORG|NET|CA|MIL|EDU)$");
            Regex name = new Regex(@"^[0-9, a-z, A-Z, \-]+$");
            Regex price = new Regex(@"^[0-9, \.]+$");

            if (url.IsMatch(urlText.Text) && name.IsMatch(nameText.Text) && price.IsMatch(priceText.Text))
            {
                itemListBox.Items.Add(nameText.Text);
                double item_Price = Convert.ToDouble(priceText.Text);
                items.Add(new Item(@itemURL.Text, itemName.Text, item_Price));
                allClear();
            }
            else
            {
                match(url, urlText, urlLabel);
                match(price, priceText, priceLabel);
                match(name, nameText, nameLabel);
            }



        }

        private void menuQuit_Click(object sender, EventArgs e)
        {
            if (MessageBox.Show("Are You Sure You Want To Quit?", "Goodbye?", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
            {
                Application.Exit();
            }
        }

        private void itemListBox_DoubleClick(object sender, EventArgs e)
        {
            if (itemListBox.SelectedItem != null)
            {
                var editor = new Edit(items);
                editor.Show();
            }
        }

        private void menuEdit_Click(object sender, EventArgs e)
        {
            var editor = new Edit(items);
            editor.Show();
        }

        private void calculateTotalToolStripMenuItem_Click(object sender, EventArgs e)
        {
            var total = new Form3(items);
            total.Show();
        }

        private void resetAllToolStripMenuItem_Click(object sender, EventArgs e)
        {
            items.Clear();
            itemListBox.ResetText();
        }

        private void Furnish_Load(object sender, EventArgs e)
        {
            foreach (Item i in items)
            {
                itemListBox.Items.Add(i.Name);
            }
        }

        private void menuOpen_Click(object sender, EventArgs e)
        {
            string filePath = "";
            if (openFile.ShowDialog() != DialogResult.Cancel)
            {
                filePath = openFile.FileName;
            }
        }
    }
}