Encrypt to Md5 or Sha1

Hello,
i need to encrypt a string to md5 or sha1,
i did this in vb long time ago.

but gave me other values then php did.
now i want to do this with C# and get the same hash codes.
Hello in php is:
Sha1 Encryption: f7ff9e8b7bb2e09b70935a5d785e0cc5d9d0abf0
Md5 Encryption: 8b1a9953c4611296a827abf8c47804d7

Can someone please help me with this
Thanks so much

Chris