C# PInvoking user32.dll on a 64 bit system

c# 64-bit pinvoke 32-bit user32
James Cadd picture James Cadd · Oct 9, 2009 · Viewed 22.8k times · Source

Is it wrong to pinvoke user32.dll on 64 bit Windows, from a 64 bit app? I've done this successfully a number of times and never had an error, but it seems contradictory. Should I look for user64.dll instead?

Answer

Mehrdad Afshari picture Mehrdad Afshari · Oct 9, 2009

The name user32.dll is misleading. It's the 64 bit version of user32.dll you're calling. The 64 bit version is located at %windir%\System32\user32.dll.

A 32-bit version is included for compatibility with 32-bit applications. It's located at %windir%\SysWOW64\user32.dll. You can inspect them using the dumpbin utility:

System32\user32.dll:

FILE HEADER VALUES
        8664 machine (x64)

SysWOW64\user32.dll:

FILE HEADER VALUES
         14C machine (x86)

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