I want to be able to search through a given HTML and find certain tags

```
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string url = "http://www.google.com";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            StreamReader sr = new StreamReader(response.GetResponseStream());
            richTextBox1.Text = sr.ReadToEnd();
            sr.Close();

        }
    }
}

```

How do I convert what I have from the StreamReader into a String so that I can do further analysis...