How to make a 'struct' Nullable by definition?

Question

struct AccountInfo {    String Username;    String Password; } 

now if I want to have a Nullable instance I should write:

Nullable<AccountInfo> myAccount = null; 

But I want make the struct Nullable by nature and it can be used like this (without use of Nullable<T>):

AccountInfo myAccount = null; 

Answer 1

You can't. Struct are considered value types, and by definition can't be null. The easiest way to make it nullable is to make it a reference type.

The answer you need to ask yourself is "Why is this a struct?" and unless you can think of a really solid reason, don't, and make it a class. The argument about a struct being "faster", is really overblown, as structs aren't necessarily created on the stack (you shouldn't rely on this), and speed "gained" varies on a case by case basis.

See the post by Eric Lippert on the class vs. struct debate and speed.