.net - Windows API Leads To Different Results Based On Name Of Unused Variable?

Everything I know about .Net programming tells me that the behavior I see here is completely impossible. Simple code:

Structure WKSTA_USER_INFO_1
Dim wkui1_username As Integer
Dim wkui1_logon_domain As Integer

[Code]....

When I put a break point in here, I see that after RtlMoveMemory, my wk1 contains a pointer to a username, and all the others are 0. This is consistant. Now, if I change Dim test As String = "" to Dim login As String = "" and run it again, wk1 contains pointers to both username and logon_domain.

If I change it to Dim login As String, it contains a pointer to only the username. Depending on what I change that (completely unused) variable name to, I get a different result.

I have always been under the impression that it cannot possibly matter what you choose to name your variable. And that declaring a variable, and then never using it, cannot possible be different from not having a variable there at all.

I've tried this on 2 computers, with consistant results (one on .Net 3.5 and one on 4.0). When I tried converting it to C#, however, I was not able to reproduce it.

I am aware, by the way, that I can just use System.Environment to get what I need about the current user information; this was old VB6 code that was automatically upgraded (and I've edited it a little to make it more trivial).