困扰3天得问题----为什么面域创建后无法进行布尔运算？？？求解

峨眉峰

   Dim region1 As Autodesk.AutoCAD.Interop.Common.AcadRegion
   Dim region2 As Autodesk.AutoCAD.Interop.Common.AcadRegion

   region1 = AcadApp.ActiveDocument.ModelSpace.AddRegion(circle)
   region2 = AcadApp.ActiveDocument.ModelSpace.AddRegion(ccc)


   region1.Boolean(Autodesk.AutoCAD.Interop.Common.AcBooleanType.acSubtraction, region2)
布尔运算不了？？？？？？？？为什么？？？？？