Doubts in Windows application for google search

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.NET3.5

.NET

Hai,

I am developing a project for google search option in the windows application.In my project I am having some doubts.Below is the sample code. I am getting the error in "webbrowser".

"An object reference is required for the non-static field, method, or property 'System.Windows.Forms.WebBrowser.GoSearch()'".<br />

similarly i am getting error in WebBrowser.GoBack(),WebBrowser.GoForward(),WebBrowser.Navigate(string).
Please rectify this.

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.IO;

namespace WINDOWS_APPLICATION_GOOGLE_SEARCH
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.Trim().Length==0)
	  {
	  label1.Text = "Please enter text to search";
	  return;
	  }
	  else
	  {
	  string sridharan = "http://www.google.com/search?q=" + textBox1.Text;
	  WebBrowser.Navigate(sridharan);
               
	  }
        }

        private void button4_Click(object sender, EventArgs e)
        {
            WebBrowser.GoBack();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            WebBrowser.GoForward();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            WebBrowser.GoSearch();
        }
    }
}