Bitcoin C# .NET API

Question

I am trying to get the address the bitcoins were last owned by or the "from" address, I know that if you send  back to that address not in all cases will the user actually get them but I still need the code for it. 

I am thinking it has something to do with

Program.b.GetTransaction()

 

If I have an address, and coins are sent to that address, I want to find out the address the coins were sent from, I have a different address for every transactions specially for this. 

Thanks in advance.