XmlReader - I need to edit an element and produce a new one

Question

I am overriding a method which has an XmlReader being passed in, I need to find a specific element, add an attribute and then either create a new XmlReader or just replace t

Answer 1

        string newvalue = "10";
        string presentvalue = "";
        string newstr = "";
        XmlReader xmlr = XmlReader.Create(new StringReader(str));

        while (xmlr.Read())
        {
            if (xmlr.NodeType == XmlNodeType.Element)
            {
                if (xmlr.Name == "priority")
                {
                    presentvalue = xmlr.ReadElementContentAsString();
                    newstr = str.Replace(presentvalue, newvalue);
                }
            }

        }

//newstr can be written back to file... that is the edited xml