Object Reference is required for the non-static field?

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C#

regular-expression

I wrote a simple program in VS 2013 C# to compare files on desktop to files in a web directory.

I am listing the local files in a textbox and want to list the remote files in a textlist with checkboxes. Then place a check next to the files in the textlist so I can then click a button to download them.

It is giving me an Object reference error when trying to add the items from regex to the textlist.

----- Current Windows Forms Code =====

namespace HardwareUtility
{
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.IO;
using System.Net;
using System.Text.RegularExpressions;

    public partial class frmFirmware : Form
    {
        public frmFirmware()
        {
            InitializeComponent();
            ftpFirmwareList.AutoResizeColumns(ColumnHeaderAutoResizeStyle.HeaderSize); 
        }
        public static string GetDirectoryListingRegexForUrl(string url)
           // get the files in the url directory and list in the textlist
        {
            if (url.Equals("http://website/subfolder/"))
            {
                return "<a href="\".*\"">(?<name>.*)</a>"; // [Ed. colouriser bug due to \""]
            }
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                {
                    string html = reader.ReadToEnd();
                    Regex regex = new Regex(GetDirectoryListingRegexForUrl(url));
                    MatchCollection files = regex.Matches(html);
                    if (files.Count > 0)
                    {
                        foreach (Match files in matches)
                        {
                            webFirmwareList.Items.Add(files.Groups[1]);
                        }
                        throw new NotSupportedException();
                    }
                }
            }
        }  
        private void frmFirmware_Load(object sender, EventArgs e)
        {
            // use to get the application directory           
           string appPath = System.IO.Directory.GetCurrentDirectory(); //Get the application directory
            
            // Combine the appPath the Firmware dir to create location path
            string firmwarePath = System.IO.Path.Combine(appPath, "Firmware\\");

            listBox1.Items.Clear();

            string[] files = Directory.GetFiles(firmwarePath);
            string[] dirs = Directory.GetDirectories(firmwarePath);

            foreach (string file in files)
            {

                listBox1.Items.Add(Path.GetFileNameWithoutExtension(file));
            }
         }
        private void okButton_Click_1(object sender, EventArgs e)
        {
            this.Close();
        }

        private void downloadButton_Click(object sender, EventArgs e)
        {
          // code to copy the new files into the local dir and delete the old file
        }
    }
}

[Edit (Matt T Heffron): wrap code in pre tags for formating]
----------

Is this the correct way to do this or is their an easier method. This is one part of many in my forms application.

thanks