COMException执行环境无效

mattran

开发环境为Win7 32位+VS2010+AutoCAD 2012，采用下面的方式打开现有dwg文件：

1. try
   
2. {
   
3.     Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.Open(filePath, false);
   
4. }
   
5. catch (Exception ex)
   
6. {
   
7.     Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor.WriteMessage(ex.ToString());
   
8. }

try<br /> {<br />     Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.Open(filePath, false);<br /> }<br /> catch (Exception ex)<br /> {<br />     Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor.WriteMessage(ex.ToString());<br /> }

但报错：执行环境无效，具体信息为：
System.Runtime.InteropServices.COMException (0x802000C8): 执行环境无效
   在 System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32
errorCode, IntPtr errorInfo)
   在 System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode)
   在 Autodesk.AutoCAD.ApplicationServices.DocumentCollection.Open(String
fileName, Boolean forReadOnly, String password)
   在 Autodesk.AutoCAD.ApplicationServices.DocumentCollection.Open(String
fileName, Boolean forReadOnly)
   在 MetroSection.HeightForm.btnImportDWG_Click(Object sender, EventArgs e) 位置
E:\Program\SZGCFY\MetroSection\HeightForm.cs:行号 50

请问这是什么原因？