Win 7 DllImport C# Odd error, Invalid access to memory location?

I notice one big difference between your dev machine and your target machine, the dev environment. Make sure you have all the necessary redistributables on the target machine.

Edit: I have seen similar issues when some dlls were compiled to different versions of the .Net framework or if they were made with different versions of Visual Studio, as the redistributables for each version are different and the latest redistributables are not exactly backwards compatible.

I had the same problem here Native loading works good. Loading from .net gives error Unable to load DLL 'my.dll': Invalid access to memory location

The problem was in DEP feature. When I switched on DEP for essential programs only, it gave no effect. But when I completely switched off DEP, and rebooted my server, error has gone. The one more thing I've done - installed latest updates for .net 4.0

The one notable thing - i didn't see any errors about DEP, just closing with "memory" error.

I've had this issue before. I think your problem is with VS trying to open the file but not having permissions to read it. You need to make sure the account you're using has access to the DLL. Try disabling UAC to see if it works, or use an Administrator account. Or try giving Full Control on the DLL to Everyone.

EDIT: Could you run VS as administrator (right click -> Run As Administrator)? Could you put the DLL onto your desktop to try? Is there a folder structure difference between your working computer and the one that's failing? Also, can the DLL run fine if you execute it outside of VS (try running it as admin as well)?

HTH

I have had similar problems before, try the following.

• Check the .NET CLR version. Are there any SPs/KBs present in your target that is not in your dev?
• Try loading the debug version of the C++ DLL. Are you able to load it? If it fails, I'd suggest starting your app under WinDBG in your target. Once the exception is hit, a simply !analyze -v will give you lots of info.
• As a next step, I'd try to reproduce this issue in a unit test environment. Are the C# samples you mentioned built for x64 VM? If not, try doing that and try running the resulting sample binary in your target. Is the issue reproducible?

I have encountered a problem with a 64bit .NET app ("Any CPU") trying to load a 32bit native DLL dependency. I don't have the error message in front of me, so I can't tell you if it is the same problem. The solution for my problem was to change my build to x86-only.

If the bit size of the DLL is changing on each box, maybe there are structure size differences, so your PInvoke signature becomes incorrect. This could easily cause a buffer overrun, and cause stack corruption in the native code.

If you're getting the error in your C# app, this message often indicates the native code did something nasty to memory that the ILM can see - check the code in/called by your DllMain routine - that is called before your call actually goes thru - if it's misbehaving, you'd see this result

@Merlyn Morgan-Graham We faced a similar problem. Where we built the .Net application with "Any CPU" build and tried using with 32 bit C++ Dll. When we run the .Net Application in 64 bit OS. It runs as 64 bit executable and hence and got similar issue. After buidling in X86 Loading, Calls to C++ Dlls worked absolutely fine. One more important thing is if you are using C++ DLL in your .Net code. There would be fair amount of marshalling, so it is important to stick to the build type (i.e. X86, any CPU or X64).

Please check the following link also: Windows Vista: Unable to load DLL 'x.dll': Invalid access to memory location. (DllNotFoundException)

The obvious, but probably lame solution would be to build C# side explicitly for 32-bit. Check how do you create out of proc host - programatically or by populating registry keys or ... could be that on other box it gets set up to either make 64-bit hosting process or attempt in-proc invocation, which means loading ... It it's a registry setting don't forget that for mixed 23/64 bit cases there are two branches to dig into.