c# - P/Invoke Calls Failing -

i have following struct defined in c++:

struct graphicsadapterdesc {     // ... constructors / operators / destructor here     define_default_constructor(graphicsadapterdesc);     define_default_destructor(graphicsadapterdesc);     allow_copy_assign_move(graphicsadapterdesc);      std::wstring adaptername;     int32_t adapternum;     std::wstring hardwarehash;      int64_t dedicatedvmem;     int64_t dedicatedsmem;     int64_t sharedsmem;      int32_t numoutputs; }; 

in c#, have 'mirror' struct declared thusly:

[structlayout(layoutkind.sequential)] public struct graphicsadapterdesc {     string adaptername;     int adapternum;     string hardwarehash;      long dedicatedvmem;     long dedicatedsmem;     long sharedsmem;      int numoutputs; }; 

i've tried careful matching widths of variables (although i'm bit unsure on strings exactly).

anyway, have following exported c method:

extern "c" __declspec(dllexport) bool getgraphicsadapter(int32_t adapterindex, graphicsadapterdesc& outadapterdesc) {     outadapterdesc = render_component.getgraphicsadapter(adapterindex);     return true; } 

and, following extern method in c# app:

[dllimport(interoputils.runtime_dll, entrypoint = "getgraphicsadapter", callingconvention = callingconvention.cdecl)] internal static extern bool _getgraphicsadapter(int adapterindex, out graphicsadapterdesc adapterdesc); 

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however, doesn't work right when call it. different result depending on whether or not i'm compiling in x64 or x86 mode (both c++ dll , c# app compiled x86 or x64):

• in x86 mode, call returns, struct has 'nonsense' values in, , strings null,
• in x64 mode, call throws nullpointerexception.

my expectation i'm doing wrong marshalling strings, , need specify 'wide-mode' characters, don't know how (or if that's right option).

thank in advance.

c++ types not compatible c# unless they're wrapped in managed c++. , you're using std::wstring cannot marshaled .net.

to interop you'll either need use wchar_t[] or whar_t* , tell c# marshal it.