How to import void * C API into C#?

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孤独总比滥情好 2021-02-20 10:17

Given this C API declaration how would it be imported to C#?

int _stdcall z4ctyget(CITY_REC *, void *);

I\'ve been able to get this far:

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  • 2021-02-20 10:52

    You can also use void* if you mark your class as unsafe.

    It really depends on what the API is looking for in that parameter.

    You can add IntPtr or Object* to get past compiler, but you will still need to pass it the correct data when you call it.

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  • 2021-02-20 11:00

    For the void* parameter you can just use an IntPtr

      [DllImport(@"zip4_w32.dll",
            CallingConvention = CallingConvention.StdCall,
            EntryPoint = "z4ctygetSTD",
            ExactSpelling = false)]
        private extern static int z4ctygetSTD(ref CITY_REC args, IntPtr ptr);
    
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  • 2021-02-20 11:08

    As far as I can tell the C declaration of z4ctyget is:

    int z4ctyget(CITY_REC *cityrec, char *zipcode);
    

    The second parameter is a 5 character ANSI string representing the zip code at which you want to start your search or "00000" to start at the beginning of the file. So your declaration should be:

    [DllImport(@"zip4_w32.dll", CharSet = CharSet.Ansi)]
    private extern static int z4ctygetSTD(ref CITY_REC args, string zipcode);
    
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