I am also trying to figure this one out.
Here is what I have done, but Autocad pauses for 12 sec while ruinning this. The search path does get changed, I just think 12 sec is excessive therefor I am sure I have done this totally wrong.
public partial class MyClass
public void STest()
AcadApplicationClass oApp = new AcadApplicationClass();
Your's code start new instance of AutoCAD!
Try instead to get current instance of AutoCAD:
Autodesk.AutoCAD.Interop.AcadApplication oApp =
Yes, all the Preferences for AutoCAD are accessible in .NET through AcadApplication.Preferences where AcadApplication is your instance of the AutoCAD Application Class.
For Preferences which can accept multiple File Path entries such as the Support File Search Path, you can feed the paths in as a single string, with each Path separated from the next by a semi-colon (no spaces). Also, do not finish with a semi-colon.
AcadApp as AcadApplication
'New up an instance of Acad or connect to a running instance here...