[quote user="George Peng"]I want to know how to use codes to open AccuDraw[/quote]
There is an AccuDraw example delivered with the MicroStation CONNECT SDK...
..\SDK\examples\Elements\AccuDrawDemo
[quote user="George Peng"]Development language is MDL[/quote]
The MicroStation CONNECT SDK provides the MicroStationAPI C++ interface. While some MDL functions remain, the API is mostly C++ classes.
For example, if you search MicroStationAPI help you will find classes for both AccuDraw and AccuSnap.