By default AutoCAD starts with a drawing open so you should always have some drawing on your screen. If the user shuts the drawing and your looking at an empty application you could just shut down that AutoCAD application and start a new one with the default drawing on the screen, something like this. I don't know if you can start a new drawing in an empty acad app. Never had to try. Somebody else might have a more viable solution.
Public WithEvents ACADApp As AutoCAD.AcadApplication
Dim acadDoc As AutoCAD.AcadDocument
Sub GetAcadApplication()
Try
ACADApp = GetObject(, "AutoCAD.Application.16")
ACADApp.Visible = True
Catch
MsgBox("Can't find AutoCAD so I'll try starting a new copy.")
Try
ACADApp = CreateObject("AutoCAD.Application.16")
ACADApp.Visible = True
Catch
MsgBox("Big Big Problem" + vbCrLf + "Closing down.", MsgBoxStyle.Critical)
End
End Try
End Try
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
GetAcadApplication()
Try
acadDoc = ACADApp.ActiveDocument
Catch
ACADApp.Quit()
GetAcadApplication()
acadDoc = ACADApp.ActiveDocument
End Try
acadDoc.Application.Documents.Open("c:/temp/test.dwg")
End Sub