string xml = "<tables><table1><col1>xyz</col1></table1></tables>";
DataSet ds = new DataSet();
ds.ReadXml(XDocument.Parse(xml).Root.Element("table1").CreateReader());
var value = ds.Tables[0].Rows[0]["col1"].ToString(); //<-- xyz
EDIT
XDocument
is inSystem.Xml.Linq
namespacethe code can be as
ds.ReadXml(XDocument.Parse(xml).Root.Elements().First().CreateReader());