I am studying C# 2.0 to get myself upto speed with .NET 2.0
I am reading “A Programmers Introduction to C# 2.0 – Apress”

There is a great new class in .NET 2:

System.Security.SecureString

 
This provides a  mutable string that is encrypted in memory.
This is ideal for passwords &c that need to be hidden for prying debuggers.