private string OpenDialogFile()
    {
        OpenFileName openFileName = new OpenFileName();

        openFileName.structSize   = System.Runtime.InteropServices.Marshal.SizeOf(openFileName);
        openFileName.filter       = "IFC文件(*.ifc)\0*.ifc";
        openFileName.file         = new string(new char[256]);
        openFileName.maxFile      = openFileName.file.Length;
        openFileName.fileTitle    = new string(new char[64]);
        openFileName.maxFileTitle = openFileName.fileTitle.Length;
        openFileName.initialDir   = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);//默认路径
        openFileName.title        = "选择所需的ifc文件";
        openFileName.flags        = 0x00080000 | 0x00001000 | 0x00000800 | 0x00000008;

        if (OpenFileName.GetSaveFileName(openFileName))
        {
            return(openFileName.file);
        }
        else
        {
            return(null);
        }
    }