[Request] Detect Text

Well i dont know how to word this but hmm ill try to show u in a fake like code and can u make a vb.net
//WITH//
textbox1, label1-2-3
//
//fake code//
if textbox1.text contains "www." then
'how would i do that?
<random code>
end if
/////////for ecample
textbox1 = http://www.youtube.com/watch?v=_4VCpTZye10
/////////
how would i do this
dim website as string = textbox1.text between "www." & .com or .net or .org
dim type as string = textbox1.text after website
dim id as string = textbox1.text between "/watch?v=" and ending

////

hope i can understand with this fake code and make it a real one plz n thz