如何把利用DataSet的GetXml()方法获得的字符串再转成DataSet对象

DataSet ds = db.ExecSqlForDataSet( strSQL );
string strDS = ds.GetXml();
......
//如何把strDS转换成DataSet对象??

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String strDS = "..."
System.IO.StringReader reader = new System.IO.StringReader(strDS);
ds.ReadXml(reader);
reader.Close();