My c# applcation is gving build errors (An object reference is required for the non-static field, method, or property )

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Xml;
using System.IO;
using System.Net;
using System.Web;
 
 
namespace Search_application
{
    public partial class queryBox : Form
    {
        public queryBox()
        {
            InitializeComponent();
 
        }
        private string SelectTextFile(string initialDirectory)
        {
            OpenFileDialog dialog = new OpenFileDialog();
            dialog.Filter = "XML files (*.xml)|*.xml";
            dialog.InitialDirectory = initialDirectory;
            dialog.Title = "Select an XML file";
            return (dialog.ShowDialog() == DialogResult.OK)
               ? dialog.FileName : null;
        }
 
        private void queryBox_Load(object sender, EventArgs e)
        {
            
        }
 
        private void textBox_TextChanged(object sender, EventArgs e)
        {
             string qr = (string)textBox.Text;
 
        }
 
        private void searchButton_Click(object sender, EventArgs e)
        {
            try
            {
                //searchListBox.Items.Clear();
 
                // Create the web request
                String query ="http://search.yahooapis.com/WebSearchService/V1/webSearch?appid=x29dfDTV34G4VzhX6WEL1SHhnMC4ZXG7qreBll.G3lxt4VnQasFS5Bznw1ccA4c- &query=";
                query += textBox.Text;
                Uri address = new Uri(query);
 
                HttpWebRequest request = WebRequest.Create(address) as HttpWebRequest;
                request.Proxy = new System.Net.WebProxy("wwwcache.lancs.ac.uk", 8080);
 
                XmlDocument xmldoc = new XmlDocument();
 
                // Get response
                using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
 
                {
                    // Get the response stream
                    StreamReader reader = new StreamReader(response.GetResponseStream());
 
                    MessageBox.Show(reader.ReadToEnd());
 
                    //xmldoc.LoadXml(reader.ReadToEnd());
                    //reader.Close();
                }
 
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error searching for data: " + ex.Message);
                
            }
        }
 
        //This code is meant to display the results on the xml page as strings
        private void resultDisplay_TextChanged(object sender, EventArgs e)
        {
            
        }
 
        private void closeButton_Click(object sender, EventArgs e)
 
        // The following code opens a message box when the 'Close' button is clicked using the mouse
        {
            bool closeButton_Click = true;
 
            if (closeButton_Click == true)
            {
                MessageBox.Show("Hope you found what you were looking for! Bye.");
                Application.Exit();                
            }
 
        }
 
        private void saveButton_Click(object sender, EventArgs e)
        //The following code saves the XML document to a file
        {
            try
            {
                SaveFileDialog sfd = new SaveFileDialog();
                SaveFileDialog.Filter = "XML|.xml";
                SaveFileDialog.FileName = "search.xml";
                SaveFileDialog.ShowDialog();
 
                FileStream fs = File.Open(SaveFileDialog.FileName, FileMode.Append, FileAccess.Write);
                XmlWriter writer = XmlWriter.Create(fs);
                XmlDocument.Save(writer);
                writer.Flush();
                writer.Close();
                fs.Flush();
                fs.Close();
            }
 
            catch (Exception E)
            {
                MessageBox.Show("Error: " + E.Message);
            }
 
        }
 
        private void openButton_Click(object sender, EventArgs e)
        {
            
        }
 
        
    }
}

                                  

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