How to find if native dll is compiled as x64 or x86?

Question:

I want to determine if native assembly is complied as x64 or x86 from a managed code application (c#). I think it must somewhere in the PE header since the OS loader needs to know this info but I couldn't find it. I prefer of course to do it in managed code but if it necessary I can use native C++.

 

Answer:

In case anyone is still looking for this (I just got here from google) there is an easy way to do this withcorflags. Open Visual Studio Command Prompt and type "corflags [your assembly]". You'll get something like this:

c:\Program Files (x86)\Microsoft Visual Studio 9.0\VC>corflags "C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll"

Microsoft (R) .NET Framework CorFlags Conversion Tool. Version 3.5.21022.8 Copyright (c) Microsoft Corporation. All rights reserved.

Version : v2.0.50727
CLR Header: 2.5
PE : PE32
CorFlags : 24
ILONLY : 0
32BIT : 0
Signed : 1

You're looking at PE and 32BIT specifically.

• AnyCpu:

  PE: PE32
  32BIT: 0

• x86:

  PE: PE32
  32BIT: 1

• x64:

  PE: PE32+
  32BIT: 0