private IsolatedStorageSettings _appSettings;

 public MainPage()

 {

 InitializeComponnent();

 _appSettings=IsolatedStorageSettings.ApplicationSettings;

 }

 if (_appSettings.Contains(key))

 {

 _appSettings[key]=value;

 }else{

 _appSettings.Add(key,value);

 }

 _appSettings.Save();

 //删除

 _appsettings.Remove(key);

 //清空

 _appSettings.Clear();

                XDocument _doc = new XDocument();

                XElement _item = new XElement(nameTxt.Text);//创建一个XML元素

                XAttribute price = new XAttribute("price", priceTxt.Text);//创建一个XML属性

                XAttribute quantity = new XAttribute("quantity", quanTxt.Text);

                _item.Add(price, quantity);//将这两个属性添加到 XML元素上

                //用_item 新建一个XML的Linq文档

                _doc = new XDocument(new XDeclaration("1.0", "utf-8", "yes"), _item);

                //创建一个本地存储的文件流

                IsolatedStorageFileStream location = new IsolatedStorageFileStream(nameTxt.Text + ".item",

                        System.IO.FileMode.Create, storage);

                //将本地存储文件流转化为可写流

                System.IO.StreamWriter file = new System.IO.StreamWriter(location);

                //将XML文件 保存到流file上 即已经写入到手机本地存储文件上

                _doc.Save(file);

                file.Dispose();//关闭可写流

                location.Dispose();//关闭手机本地存储流