AutocAD crash when open file

[Anonymous]

Autocad Ver:2012.My code:
namespace testCADOpen
{
    public class Class1
    {
        [CommandMethod("openfile")]
        public void openFile()
        {
            DocumentCollection acDocMgr = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager;
            string strFileName = @"E:\test.dwg";
            if (File.Exists(strFileName))
            {
                acDocMgr.Open(strFileName, false);
            }
        }
    }
}

triggle the err  message when debug in visual studio.(1.start vs,2 start debug ,3 netload testCADOpen.dll 4 openfile, Err)

It's no problem when netload the dll from Auocad directly.(1. start AutoCAD ,2 netload testCADOpen.dll 3 openfile, Ok)