[DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
      static extern bool InternetGetCookieEx(string pchUrl, string pchCookieName, StringBuilder pchCookieData, ref System.UInt32 pcchCookieData, int dwFlags, IntPtr lpReserved);
      private static string GetCookieString(string url)
      {
          uint datasize = 1024;
          StringBuilder cookieData = new StringBuilder((int)datasize);
          if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x2000, IntPtr.Zero))
          {
              if (datasize < 0)
                  return null;
              cookieData = new StringBuilder((int)datasize);
              if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x00002000, IntPtr.Zero))
                  return null;
          }
          return cookieData.ToString();
      }
      private void webBrowser1_DocumentCompleted_1(object sender, WebBrowserDocumentCompletedEventArgs e)
      {
          richTextBox1.Text = string.Empty;
          if (cbcookie.Checked)
          {
              if (checkBox1.Checked)
              {
                  richTextBox1.Text = GetCookieString(textBox1.Text.Trim());
              }
              else
              {
                  richTextBox1.Text = webBrowser1.Document.Cookie;
              }
          }
      }