DllNotFoundException for native DLL in 2019.x

Hi there,

I just spent three days working on a weird issue, and since I found no resources at all on this, I just wanted to leave my findings here.

I was using a native DLL in my project, like this:

Code (CSharp):

1. #if UNITY_IPHONE || UNITY_XBOX360
2.         private const string dll = "__Internal";
3. #else
4.         private const string dll = "name-of-the.dll";
5. #endif

followed by one or more

Code (CSharp):

1. [DllImport(dll)]
2. static extern void SomeExternMethod();

This is in accordance to the manual page about native DLLs with the addition of XBox360 as a platform that also has one big "__Internal" dll. To be honest, I don't remember where I found that additional bit of information.

This code worked fine for years now, but starting with Unity 2019, I got DllNotFoundExceptions with every method call. Since the (linked) manual page doesn't mention anything about this, it took me some while to find out that i needed to switch to "__Internal" entirely, so my new code looks like this:

Code (CSharp):

1. #if UNITY_2019_1_OR_NEWER || UNITY_IPHONE || UNITY_XBOX360
2.         private const string dll = "__Internal";
3. #else
4.         private const string dll = "name-of-the.dll";
5. #endif

So, apart from maybe helping someone else with that issue, I was wondering if anyone had an idea whether this is

• a bug that existed for a whole year without being discovered (as I said, I found nothing on this for days),
• some newly available Mono setting or something that I'd have to change, or
  
• the documentation not having been updated properly.

If noone slaps me on the forehead about some weird mistake I made, I'll report this as a bug within the next few days. Until then, maybe this little fix helps someone searching their butt off

 

The bug is reported, I'll relay updates about it to this thread.