SQL & PL/SQL

Need to create a routine in plsql to accomplish the following that is currently in c#:

string baseString = (Code ?? "")

                                   + (UserNumber ?? "" )

                                   + (Role ?? "" )

                                   + (FirstName ?? "" )

                                   + (LastName ?? "" )

byte[] bytes = System.Text.Encoding.UTF8.GetBytes(baseString);

byte[] hash = new System.Security.Cryptography.SHA256Managed().ComputeHash(bytes);