将 xml 文件 转为 DataTable

         private static DataTable CreateDataTable(string table) {
             DataSet dataSet = new DataSet();
             string dataFile = FilesHelper.FindingFileName(Application.StartupPath, "Data\\Mail.xml");
             if(dataFile != string.Empty) {
                 FileInfo fi = new FileInfo(dataFile);
                 dataSet.ReadXml(fi.FullName);
                 return dataSet.Tables[table];
             }
             return null;
         }