Access the same instance of Internet Explorer window

First you need to create a Windows Forms application using Visual Studio and on the Form, add a TextBox and a Button control. Also, double click on the button control to wirte its click event handler.

You also need to import two namespacces by adding "using SHDocVw;" and "using System.Runtime.InteropServices;" to the top of your code.

You will probably need to add the Microsoft Internet Controls reference as well.

WebBrowserApp webBrowser = null;
InternetExplorer explorer = new InternetExplorerClass();
ShellWindows shWin = new ShellWindows();

public Form1()
{
   InitializeComponent();
   webBrowser = (IWebBrowserApp)explorer;
}

private void button1_Click(object sender, EventArgs e)
{
   //open browser to url typed into text box
  IEOpenOnURL(textBox1.Text);
}

public void IEOpenOnURL(string url)
{
  object o = null;
  bool b = false;

  //check if window is already open
  foreach (InternetExplorer ies in shWin)
  {

     if (ies.HWND == webBrowser.HWND)
      b = true;
   }

  try
  {

    if (b)
    {
      webBrowser .Visible = true;
      webBrowser .Navigate(url, ref o, ref o, ref o, ref o);
    }
    else
    {
      //its not open so create new instance
      explorer = new InternetExplorerClass();
      webBrowser = (IWebBrowserApp)explorer;
      webBrowser .Visible = true;
      webBrowser .Navigate(url, ref o, ref o, ref o, ref o);
    }
  }
  catch (Exception)
  { // implement your exception handling here
  }
}