Silverlight实用窍门系列：74.Silverlight使用Perst数据库Demo

　　Perst是一个简单、快速、便捷的面向Java和.Net的数据库。它可以直接将.net对象存储，在Silverlight不需要web service的方式进行读写，而是直接读写。

　　本文将编写一个实例进行perst的操作，下载一个PerstSilverlight.dll，然后引用它。

　　首先：在App.xaml.cs中Application_Startup()中建立Perst数据库的实例，在Application.Exit()中关闭Perst数据库。

        private void Application_Startup(object sender, StartupEventArgs e)
        {
            //应用程序开启时打开数据库
            Storage instanse = StorageFactory.Instance.CreateStorage();
            //初始化数据库文件为1M
            instanse.SetProperty("perst.file.extension.quantum", 1024 * 1024);
            //数据库大小不够时，每次增加512K
            instanse.SetProperty("perst.extension.quantum", 512 * 1024);
            instanse.Open("SLDemo.dbs");
            db = new Database(instanse);
            this.RootVisual = new MainPage();
        }

        private void Application_Exit(object sender, EventArgs e)
        {
            //应用程序关闭时关闭数据库连接
            db.Storage.Close();
        }

　　其次：建立一个实体类继承于Persistent，定义为索引的字段必须设置为Public。

    /// <summary>
    /// 城市类
    /// </summary>
    public class City : Persistent
    {
        //定义为索引
        [FullTextIndexable]
        public string _CityName;

        /// <summary>
        /// 城市名称
        /// </summary>
        public string CityName
        {
            get { return _CityName; }
            set { _CityName = value; }
        }

        [FullTextIndexable]
        public string _CityNum;

        /// <summary>
        /// 城市电话区号
        /// </summary>
        public string CityNum
        {
            get { return _CityNum; }
            set { _CityNum = value; }
        }

        public override void OnLoad()
        {
            base.OnLoad();
        }

        //删除
        public override void Deallocate()
        {
            base.Deallocate();
        }
    }

　　再次：实现前台界面的事件，并实现它。

    public partial class MainPage : UserControl
    {

        public MainPage()
        {
            InitializeComponent();

        }

        private void GetNum_1(object sender, RoutedEventArgs e)
        {
            BindCity();
        }

        /// <summary>
        /// 绑定所有的城市，并且按照CityNum排序
        /// </summary>
        private void BindCity()
        {
            List<City> list = App.db.Select<City>("order by CityNum").ToList();
            this.dgrid.ItemsSource = list;
        }

        /// <summary>
        /// 查找到021号码的区号对象并且删除
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void DeleteNum_2(object sender, RoutedEventArgs e)
        {
            City city = App.db.Select<City>("CityNum='021'").FirstOrDefault();
            city.Deallocate();
            App.db.Storage.Commit();
            BindCity();
        }

        /// <summary>
        /// 查找到020区号的对象进行修改
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void EditNum_4(object sender, RoutedEventArgs e)
        {
            City city = App.db.Select<City>("CityNum='020'").FirstOrDefault();
            city.CityName = "上海市";
            city.Store();
            App.db.UpdateFullTextIndex(city);
            BindCity();
        }

        /// <summary>
        /// 添加数据
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void AddNum_3(object sender, RoutedEventArgs e)
        {
            App.db.AddRecord(new City() { CityName = "广州", CityNum = "021" });
            App.db.AddRecord(new City() { CityName = "北京", CityNum = "010" });
            App.db.AddRecord(new City() { CityName = "上海", CityNum = "020" });
            App.db.AddRecord(new City() { CityName = "成都", CityNum = "028" });
            App.db.Storage.Commit();
        }
    }

　　最后我们来看前台界面Xaml如下：

    <Grid x:Name="LayoutRoot" Background="White">
        <sdk:DataGrid Name="dgrid" HorizontalAlignment="Left" Height="181" 
                Margin="10,80,0,0" VerticalAlignment="Top" Width="338"/>
        <Button Content="增加数据" HorizontalAlignment="Left" Margin="42,10,0,0"
                VerticalAlignment="Top" Width="75" Click="AddNum_3"/>
        <Button Content="获取值" HorizontalAlignment="Left" Margin="160,10,0,0"
                VerticalAlignment="Top" Width="75" Click="GetNum_1"/>
        <Button Content="修改值" HorizontalAlignment="Left" Margin="42,48,0,0"
                VerticalAlignment="Top" Width="75" Click="EditNum_4"/>
        <Button Content="删除值" HorizontalAlignment="Left" Margin="160,48,0,0"
                VerticalAlignment="Top" Width="75" Click="DeleteNum_2"/>
    </Grid>

　　下面是效果图片，如需源码请点击 SLPerstDemo.rar 下载。