Structure -v- UDT (in vb6)

Hi

I am starting to convert a large vb6 program to dot.net. I am starting with structures of my data files.

In vb6 I had (as an example)

Public Type Bloggs
BusName As String *30
Postcode As String *6
Opening capital as Currency 'which is 8 bytes
etc.

I realise that I need eg

Public structure Bloggs
Public BusName As String...

There I run into trouble, as I can't seem to define the length of the string(s). That matters because I want to read existing datafiles and keep the fields in step.