VS 2010 Delete Text

So what i actually need is something like this
First, download the source from a website

Dim request As System.Net.HttpWebRequest = System.Net.HttpWebRequest.Create(TextBox1.Text)
Dim response As System.Net.HttpWebResponse = request.GetResponse()
Dim sr As System.IO.StreamReader = New System.IO.StreamReader(response.GetResponseStream())
Dim sourcecode As String = sr.ReadToEnd()
TextBox1.Text = sourcecode

Second, remove all the source except from any word that contains www.example.com
Third,remove all the websites that contain www.example.com/example/

Thanks for helping