gistfile1.cs

public static void AppendQuestions(string question,
            string answer, string case1, string case2, string difficulty)
        {
            try {

                XmlDocument XmlDoc = new XmlDocument();
                XmlDoc.Load(XML_FILE_PATH);
                XmlElement newElem = XmlDoc.CreateElement("task");

                XmlAttribute difficultyAttribute = XmlDoc.CreateAttribute("stage");
                difficultyAttribute.Value = difficulty;
                newElem.Attributes.Append(difficultyAttribute);

                newElem.InnerXml = "<question></question><answer></answer><case1></case1><case2></case2>";
                //XmlText txtNode = XmlDoc.CreateTextNode("A BRIEF HISTORY OF TIME");
                //newElem.FirstChild.AppendChild(txtNode);
                //newElem.AppendChild(doc.CreateWhitespace("\r\n")); // Linefeed
                newElem["question"].InnerText = question;
                newElem["answer"].InnerText = answer;
                newElem["case1"].InnerText = case1;
                newElem["case2"].InnerText = case2;

                XmlDoc.DocumentElement.LastChild.AppendChild(newElem);
                XmlDoc.Save(XML_FILE_PATH);
            }
            catch (XmlException xmlEx)        // Handle the Xml exceptions here.         
            {
                Console.WriteLine("{0}", xmlEx.Message);
            }
        }