This won't work. The named pipe facility in .NET is NOT the same as a DBMS_PIPE. They are not compatible, so you would have to have Oracle execute .NET code to pull data from the named pipe. Since this can't happen (easily), it's easier just to use the DBMS_PIPE and have the client use that.
So, if you create a package that can read/write to the DBMS_PIPE and connect your .NET client to the database and call that package then you should be good to go. See
here for more information.