getting text from editbox

[MPrestonf12]

char *buf[20];
	SendMessage(editbx,EM_GETLINE,0,buf);
	MessageBox(NULL,buf, "Interest App", MB_OK | MB_ICONINFORMATION);

im trying to retrieve text from a editox called "editbx" and display it in a messagebox. Anyone know how to. I looked it up on MSDN and it was a bit confusing