OpenXML操作Excel提示SharedStringTablePart序列为空

Question

using excel=DocumentFormat.OpenXml.Spreadsheet;
using office=DocumentFormat.OpenXml.Office2010;
using pack=DocumentFormat.OpenXml.Packaging;
using oxml=DocumentFormat.OpenXml; pack.SpreadsheetDocument tmDoc = pack.SpreadsheetDocument.Open(exclFile, false);
为什么下面这条语句提示SharedStringTablePart序列为空，但SharedStringTable肯定存在的 pack.SharedStringTablePart tmTbPartStation = tmDoc.GetPartsOfType<pack.SharedStringTablePart>().First()
openxmlexceloffice