How to import void * C API into C#?

Question

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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Answer 1

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.

Answer 2

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);

Answer 3

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);