AutoCAD .NET :: Create New DWG From Template File (DWT) And Save

Current development env:  AutoCAD 2012, VS 2010, ObjectARX.Net (2012)

My target:  in AutoCAD pops a dialog, select filename (related to our internal projects) string, then it will create a DWG file from a template DWT file. Then some operation like insert elements into the DWG file and then SAVE (with the filename assigned).

Here is the code I currently implemented:

class DWGWritter
{
const string TemplateFile = @"C: empMyTemplate.dwt";

[Code]....

Well it doesn't work on either of #1-4

#1 give out "eFileInternalErr" exception, which I found the answer - you can't call save() if it's open from exist file

#2 works ... but it just save the contents we write to the database but won't save template file contents, ie. we have put in layers inside the template file but they doesn't save to the new file

#3 give out "drawing is busy" error, no clue why it's "busy" ...

#4 give out same error as #3