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Answer 1

+1 A:

Use GetEnvironmentVariable to look for the PROCESSOR_ARCHITEW6432 variable. If it doesn't exist, you must be running 32bit:

bool is64bit = !string.IsNullOrEmpty(
    Environment.GetEnvironmentVariable("PROCESSOR_ARCHITEW6432"));

EDIT:

Thanks to Hans Passant for pointing out the error in using the PROCESSOR_ARCHITECTURE variable.

GenericTypeTea 2010-09-03 12:06:00

Have you actually tried this? Wow64 is not that easily defeated, emulation covers every corner. Except IsWow64Process and GetNativeSystemInfo.

Hans Passant 2010-09-03 12:27:00

@Hans Passant - Copied from a production system. Should I be worried?

GenericTypeTea 2010-09-03 12:37:28

Go ahead, worry.

Hans Passant 2010-09-03 12:39:51

@Hans Passant - Was a serious question actually. I thought it pulled the value from 'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment\PROCESSOR_ARCHITECTURE'? How can that be wrong?

GenericTypeTea 2010-09-03 12:41:09

Registry virtualization is also taken care of by Wow64.

Hans Passant 2010-09-03 12:53:27

@Hans Passant - Update the answer. Hopefully that's better.

GenericTypeTea 2010-09-03 13:00:32

Yes, better, I know that one normally exists. What I'm not so sure about is that it is *guaranteed* to exist. Not close to an x64 machine right now to check, but avoid relying on registry keys that initialize the session. If the key is actually in the registry, rather than emulated by Wow64, it might not be there some day on some machine. The linked thread is a reliable way.

Hans Passant 2010-09-03 13:08:40

@Hans Passant - Thank you for your advice, much appreciated :)

GenericTypeTea 2010-09-03 13:09:54

Answer 2

A:

http://stackoverflow.com/questions/336633/how-to-detect-windows-64-bit-platform-with-net

dmitko 2010-09-03 12:06:14

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