Using AppDomains to Parallelize Non-thread-safe DLL

Question

I have an unmanaged C++ DLL that my .NET application uses via p/invoke. The method that I need from this DLL is fairly time consuming and I would like to parallelize the method calls. The problem is that it uses a bunch of statics and globals, so it is not thread-safe (and can't be changed). My plan was to overcome this non-thread-safe issue by calling the unmanaged DLL from multiple AppDomains in parallel.

I can call the unmanaged code from the multiple AppDomains without any problems as long as I don't do it in parallel, but as soon as I make the calls in parallel, I get an AccessViolationException. I am using Parallel.For() to make the parallel calls.

Is it possible to make a non-thread-safe unmanaged DLL "thread-safe" by simply making the calls from multiple AppDomains?

Answer 1

Calling the native method from multiple AppDomain instances won't help you at all here. AppDomain boundaries don't apply to native DLL's and they won't provide any benefit