Unable to load .NET assembly in Powershell

Question

I have an SDK from a vendor, of which I am using a particular DLL which provides COM interop with the vendor system.

I have successfully created a POC C# project using classes in this DLL. I add the reference to the DLL, add the using clause for the namespace, voila. My target framework is 4.0 and platform is x86.

I now want to do use Powershell to achieve the same task, however I cannot get the DLL to load.

When I try

add-type -path $myDLL

or

[System.Reflection.Assembly]::LoadFrom($myDLL)

I get the following exception:

add-type : Could not load file or assembly 'file:///C:\Program Files 
(x86)\Interwoven\WorkSite\IManage.dll' or one of its dependencies. The module was expected to contain 
an assembly manifest.
At line:2 char:1
+ add-type -path $myDLL
+ ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Add-Type], BadImageFormatException
    + FullyQualifiedErrorId : System.BadImageFormatException,Microsoft.PowerShell.Commands.AddTypeComma 
   nd

I have confirmed I'm running in Powershell x86 and i even tried forcing CLRVersion to match the DLL ImageRuntimeVersion using the method described here with no success.

What else am I missing here? Thanks!

PS H:\> $env:processor_architecture
x86
PS H:\> $psversiontable

Name                           Value                                                                    
----                           -----                                                                    
PSVersion                      3.0                                                                      
WSManStackVersion              3.0                                                                      
SerializationVersion           1.1.0.1                                                                  
CLRVersion                     4.0.30319.34209                                                          
BuildVersion                   6.2.9200.16398                                                           
PSCompatibleVersions           {1.0, 2.0, 3.0}                                                          
PSRemotingProtocolVersion      2.2

You need to run the 32 bit powershell console. C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe You can't load a 32 bit dll in a 64 bit process or vice versa unless the dll was compiled for Any Cpu, in which case .Net JIT's it to the appropriate platform. Which is not the case with a com interop dll. — Ryan Mann
– Ryan Mann, Commented Jul 21, 2015 at 17:39
Note that $env:Processor_Architecture tells you the processor architecture not the process bitness. Of course, since it is x86, there is no possibility of running a 64-bit process by mistake. Use [Environment]::Is64BitProcess to tell if the current process is 64-bit. — Mike Zboray
– Mike Zboray, Commented Jul 21, 2015 at 17:57

Keith Hill · Accepted Answer · 2015-07-21 17:29:30Z

4

The major clue here is the BadImageFormatException. This means you are either trying to load a 32-bit dll into a 64-bit PowerShell process or a 64-bit dll into a 32-bit PowerShell process.

Is the vendor providing the interop DLL you are loading or are you generating it with a tool like tlbimp? Usually these DLLs are architecture neutral (Any CPU) unless they need to pinvoke to a dll or load a COM dll in process.

answered Jul 21, 2015 at 17:29

Keith Hill

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3 Comments

Yevgeniy Over a year ago

yes, but I check my $env:PROCESSOR_ARCHITECTURE is x86, which matches my C# project build platform target. I have tried loading this in x64 poweshell version just for the hell of it with same result. If the process bit-ness (?) matches the one of the DLL, what else could it be? The vendor is providing the DLL.

Mike Zboray Over a year ago

BadImageFormatException can occur for multiple reasons and the error message here indicates a different cause. The OP has tried to load an unmanaged dll as a .NET dll. The same error occurs (with the same message) if you try to load kernel32.dll in a 32 or 64-bit process.

Keith Hill Over a year ago

The question states that it is a C# project. However, if that project uses another library that pinvokes a native DLL or the project directly pinvokes a native DLL, then this exception will occur. If there is no need for pinvoking native DLLs then the project should target Any CPU with "prefer 32-bit" unchecked for maximum flexibility.

b_levitt · Accepted Answer · 2017-10-19 15:29:45Z

1

In my case I had a content replacement script that was corrupting the dll. However, this was complicated by the fact that Add-Type seems to cache assemblies, even ones that failed to load. I replaced the dll with a good one and it continued to fail until I tried to load it from a different location (I imagine closing the powershell ISE would have also fixed it).

answered Oct 19, 2017 at 15:29

b_levitt

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