pass C# string to C++ dll fails in Release build

Question

I have a C++ dll with simple function like

#ifdef BUILDING_THE_DLL
#define EXPORTED __declspec(dllexport)
#else
#define EXPORTED __declspec(dllimport)
#endif
 ...
EXPORTED void AddSetting(char *key, char *value)

And a C# project with function declaration:

[DllImport("pers.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern void AddSetting(string key, string value);

Everything works perfectly well while C# project is build in Debug mode. In Release build an exception is fired: "An attempt was made to load a program with an incorrect format."

Any ideas?

UPD: In C# project Platform target was set to x86 in Debug mode and Any CPU in Release. I've changed to x86 in Release and it was the solution. Thanks a lot to Matt.

Answer 1

You need specify to use the ansi format of the string, by default. it is unicode. It should be :

[DllImport("pers.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet::Ansi)]
public static extern void AddSetting(string key, string value);

Also, if the function "AddSetting" modifies the strings, you need to use StringBuilder in C#. Please refer this MSDN article for details.