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;
        }