如何把Excel文件中的多张表导入到一个DataSet中？请大虾指教

/// <summary>
        /// 从Excel中获取数据.(无须指定表名，返回的DataSet包含此Excel中所有的表).
        /// </summary>
        /// <param name="filePath">Excel物理路径.</param>
        /// <returns>DataSet:Excel中表的记录集合.</returns>
        public DataSet ReadExcle(string filePath, out string msg)
        {
            string strSql = string.Empty;
            msg = string.Empty;
            DataSet ds = new DataSet();
            DataTable dt = null;
            OleDbDataAdapter adapter=null;
            string strTableName = string.Empty;
            if (filePath != string.Empty)
            {
                try
                {
                    //判断是否为Xls文件.
                    if (!filePath.Substring(filePath.Length - 3, 3).Equals("xls"))
                    {
                        throw new Exception(ImportConst.ErrorMessage_NoExcelFile);
                    }
                    OleDbConnection conn = new OleDbConnection(string.Format(strConnectionString, filePath));
                    conn.Open();
                    //获取XML文件Schema信息.
                    DataTable dtschema = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                    if (dtschema != null && dtschema.Rows.Count > 0)
                    {
                        //遍历Excel中所有的表
                        foreach (DataRow row in dtschema.Rows)
                        {
                            strTableName = row[2].ToString().Trim(new char[] { '\'' });
                            if (IsTable(strTableName))
                            {
                                dt = new DataTable(strTableName.Replace('$', ' '));
                                if (strTableName.IndexOf(" ") != -1)
                                {
                                    strSql = string.Format("select top 4000 * from ['{0}']", strTableName);
                                }
                                else
                                {
                                    strSql = string.Format("select top 4000 * from [{0}]", strTableName);
                                }
                                adapter = new OleDbDataAdapter(strSql, conn);
                                adapter.Fill(dt);
                                ds.Tables.Add(dt);
                            }
                        }
                    }
                    conn.Close();
                }
                catch (Exception Ex)
                {
                    msg += Ex.Message + "$";
                }
            }
            else
            {
                msg += ImportConst.ErrorMessage_NullPath + "$";
            }
            return ds;        }
        /// <summary>
        /// 判定是否为Excel中包含记录的表.(排除掉打印区域等表格.e.g xx$print Area)
        /// </summary>
        /// <param name="tableName">Excel中获取到的表名.</param>
        /// <returns></returns>
        protected bool IsTable(string tableName)
        {
            bool blIsTable = false;
            if (tableName != string.Empty)
            {
                int nIndex = tableName.LastIndexOf("$");
                if (nIndex!=-1&&tableName.Length-1==nIndex)
                {
                    blIsTable = true;
                }
            }
            return blIsTable;
        }