How to determine if a .NET assembly was built for

Question

I've got an arbitrary list of .NET assemblies.

I need to programmatically check if each DLL was built for x86 (as opposed to x64 or Any CPU). Is this possible?

Answer 1

A more advanced application for that you can find here: CodePlex - ApiChange

Examples:

C:\Downloads\ApiChange>ApiChange.exe -CorFlags c:\Windows\winhlp32.exe
File Name; Type; Size; Processor; IL Only; Signed
winhlp32.exe; Unmanaged; 296960; X86

C:\Downloads\ApiChange>ApiChange.exe -CorFlags c:\Windows\HelpPane.exe
File Name; Type; Size; Processor; IL Only; Signed
HelpPane.exe; Unmanaged; 733696; Amd64

Answer 2

Just for clarification, CorFlags.exe is part of the .NET Framework SDK. I have the development tools on my machine, and the simplest way for me determine whether a DLL is 32-bit only is to:

1. Open the Visual Studio Command Prompt (In Windows: menu Start/Programs/Microsoft Visual Studio/Visual Studio Tools/Visual Studio 2008 Command Prompt)

2. CD to the directory containing the DLL in question

3. Run corflags like this: corflags MyAssembly.dll

You will get output something like this:

    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  : 3
ILONLY    : 1
32BIT     : 1
Signed    : 0

As per comments the flags above are to be read as following:

• Any CPU: PE = PE32 and 32BIT = 0
• x86: PE = PE32 and 32BIT = 1
• 64-bit: PE = PE32+ and 32BIT = 0

Answer 3

[TestMethod]
public void EnsureKWLLibrariesAreAll64Bit()
{
    var assemblies = Assembly.GetExecutingAssembly().GetReferencedAssemblies().Where(x => x.FullName.StartsWith("YourCommonProjectName")).ToArray();
    foreach (var assembly in assemblies)
    {
        var myAssemblyName = AssemblyName.GetAssemblyName(assembly.FullName.Split(',')[0] + ".dll");
        Assert.AreEqual(ProcessorArchitecture.MSIL, myAssemblyName.ProcessorArchitecture);
    }
}

Answer 4

Below is a batch file that will run corflags.exe against all dlls and exes in the current working directory and all sub-directories, parse the results and display the target architecture of each.

Depending on the version of corflags.exe that is used, the line items in the output will either include 32BIT, or 32BITREQ (and 32BITPREF). Whichever of these two is included in the output is the critical line item that must be checked to differentiate between Any CPU and x86. If you are using an older version of corflags.exe (pre Windows SDK v8.0A), then only the 32BIT line item will be present in the output, as others have indicated in past answers. Otherwise 32BITREQ and 32BITPREF replace it.

This assumes corflags.exe is in the %PATH%. The simplest way to ensure this is to use a Developer Command Prompt. Alternatively you could copy it from it's default location.

If the batch file below is run against an unmanaged dll or exe, it will incorrectly display it as x86, since the actual output from Corflags.exe will be an error message similar to:

corflags : error CF008 : The specified file does not have a valid managed header

@echo off

echo.
echo Target architecture for all exes and dlls:
echo.

REM For each exe and dll in this directory and all subdirectories...
for %%a in (.exe, .dll) do forfiles /s /m *%%a /c "cmd /c echo @relpath" > testfiles.txt

for /f %%b in (testfiles.txt) do (
    REM Dump corflags results to a text file
    corflags /nologo %%b > corflagsdeets.txt

   REM Parse the corflags results to look for key markers   
   findstr /C:"PE32+">nul .\corflagsdeets.txt && (      
      REM `PE32+` indicates x64
        echo %%~b = x64
    ) || (
      REM pre-v8 Windows SDK listed only "32BIT" line item, 
      REM newer versions list "32BITREQ" and "32BITPREF" line items
        findstr /C:"32BITREQ  : 0">nul /C:"32BIT     : 0" .\corflagsdeets.txt && (
            REM `PE32` and NOT 32bit required indicates Any CPU
            echo %%~b = Any CPU
        ) || (
            REM `PE32` and 32bit required indicates x86
            echo %%~b = x86
        )
    )

    del corflagsdeets.txt
)

del testfiles.txt
echo.

Answer 5

DotPeek from JetBrians provides quick and easy way to see msil(anycpu), x86, x64

Answer 6

Another way to check the target platform of a .NET assembly is inspecting the assembly with .NET Reflector...

@#~#€~! I've just realized that the new version is not free! So, correction, if you have a free version of .NET reflector, you can use it to check the target platform.