Function pointer in DLL call - how to handle in C#? -

i'm using native dll called out of c# application. 1 of dll-functions defined this:

int set_line(const int width,fct_line_callback callback) 

fct_line_callback defined as

typedef int (*fct_line_callback)(double power,void *userdata); 

so how can use function out of c#-application? there way define c# method used callback-function dll-call?

thanks!

you have declare delegate type matches native function pointer. should this:

[unmanagedfunctionpointer(callingconvention.cdecl)] delegate int fct_line_callback(double power, intptr userdata); 

now can write pinvoke declaration:

[dllimport("foo.dll", callingconvention = callingconvention.cdecl)] extern static int set_line(int width, fct_line_callback callback); 

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if callback can made while set_line() executing calling native function simple:

public void setline(int width) {     set_line(width, mycallback); } private void mycallback(double power, intptr userdata) {     // etc... } 

however, if callback can made after set_line() executed, in other words when native code stores function pointer, have make sure garbage collector cannot collect delegate object. simplest way storing object in static variable:

static class wrapper {     private static fct_line_callback callback = mycallback;     public static void setline(int width) {         set_line(width, callback);     }     private static int mycallback(double power, intptr userdata) {         // etc...     } }