Hi Mohammad,
[quote user="Mohammad Aryafar"]I have searched for topics related to rasters but they either working with active model[/quote]
... which is the first sign that to work with rasters in work DGN is not standard task.
[quote user="Mohammad Aryafar"]If I use mdlWorkDgn_openFile to open an existing model, will this be my current active model?[/quote]
As Jon commented already, the answer is "no". The function is called "WorkDgn", not "ActiveDgn".
[quote user="Mohammad Aryafar"]If no, what is the correct method to open an existing model and making it the active model.[/quote]
Use mdlSystem_newDesignFile or mdlSystem_newDesignFileAndModel.
With regards,
Jan