how to use the function of PgDrawILineCx ()

I want to draw a line in ptraw .when I press the button of a dialog
int PgDrawILineCx( void *dc, int x1, int y1, int x2, int y2 );
I don’t know what’s dc. I hava a try ABW_PtRaw1.but when I press the
button, the whole program exit.
who can help me . Thanks!

PgDrawILine() work on the current draw context
PgDrawILineCx() work on the given context dc