WP之Sql Server CE数据库
如何在WP8中进行数据存储，你首先想到应该是独立存储，但是独立存储似乎存储文件更方便，如果我们希望像处理对象的形式，该怎么办呢，答案就是Sql Server CE。
Sql Server CE并不是新鲜东西，它是专门用在移动端的一个工具，它和SQLServer有很大的不同，SQLServer中我们使用Sql语句，而Sql Server CE则要使用Linq处理。
一、创建表
/// <summary> /// 员工表 /// </summary> [Table] class EmployeeTable : INotifyPropertyChanged, INotifyPropertyChanging { private int _employeeId; /// <summary> /// 员工Id /// </summary> [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)] public int EmployeeId { get { return _employeeId; } set { if (_employeeId != value) { OnPropertyChanging("EmployeeId"); _employeeId = value; OnPropertyChanged("EmployeeId"); } } } private string _employeeName; /// <summary> /// 员工名称 /// </summary> [Column] public string EmployeeName { get { return _employeeName; } set { if (_employeeName != value) { OnPropertyChanging("EmployeeName"); _employeeName = value; OnPropertyChanged("EmployeeName"); } } } private string _employeeDesc; /// <summary> /// 员工简介 /// </summary> [Column] public string EmployeeDesc { get { return _employeeDesc; } set { if (_employeeDesc != value) { OnPropertyChanging("EmployeeDesc"); _employeeDesc = value; OnPropertyChanged("EmployeeDesc"); } } } public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } public event PropertyChangingEventHandler PropertyChanging; private void OnPropertyChanging(string propertyName) { if (PropertyChanging != null) { PropertyChanging(this, new PropertyChangingEventArgs(propertyName)); } } }
一张员工表，有三个属性。类需要加上Table特性，如果你使用过Linq to sql，那么整个特性应该是见过的；另外就是对每个属性需要使用Column特性进行标注；最最重要的一点，类要实现自INotifyPropertyChanged, INotifyPropertyChanging，这两个接口主要是为了通知，同时在类中实现着两个接口的时间即可，并且在属性的Set中进行调用就ok了。
二、上下文对象类(用于操作数据，和数据库交互)
/// <summary> /// 上下文对象类 /// </summary> class EmployeeDataContext:DataContext { //数据库连接字符串 public static string DBConnectionString = "Data Source=isostore:/Employee.sdf"; public EmployeeDataContext(string connectionString) : base(connectionString) { } //员工信息表 public Table<EmployeeTable> Employees; }
就是一般的类，只不过继承自DataContext，这个和Linq to sql中的上下文对象同一个基类。类中有一个连接字符串属性，同时构造函数支持传入一个连接字符串，另外就是有我们上文中创建的表的一个Table类型的集合，表示一个集合类型。
三、数据列表类(此类大家也可以没有，因为对于集合的处理，大家可以根据自己的需要进行修改)
/// <summary> /// 列表集合 /// </summary> class EmployeeCollection : INotifyPropertyChanged { private ObservableCollection<EmployeeTable> _employeeTables; /// <summary> /// 员工列表集合 /// </summary> public ObservableCollection<EmployeeTable> EmployeeTables { get { return _employeeTables; } set { if (_employeeTables != value) { _employeeTables = value; OnPropertyChanged("EmployeeTables"); } } } public void UpdateEmployee(EmployeeTable employee) { var oldEmployee = EmployeeTables.Where(e => e.EmployeeId == employee.EmployeeId).FirstOrDefault(); oldEmployee.EmployeeName = employee.EmployeeName; oldEmployee.EmployeeDesc = employee.EmployeeDesc; } public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } }
类中只有一个Employee的集合和一个用于更新对象的方法，以及实现自INotifyPropertyChanged的内容。
四、使用
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"> <Grid Margin="0,0,0,385"> <Grid.ColumnDefinitions> <ColumnDefinition Width="*" /> <ColumnDefinition Width="Auto" /> </Grid.ColumnDefinitions> <TextBlock FontSize="30" Height="37" HorizontalAlignment="Left" Margin="12,18,0,0" Name="textBlock1" Text="员工名字:" VerticalAlignment="Top" /> <TextBox Name="name" Text="" Margin="145,0,6,144" /> <TextBlock FontSize="30" Height="52" HorizontalAlignment="Left" Margin="18,74,0,0" Name="textBlock2" Text="简介：" VerticalAlignment="Top" /> <TextBox Height="79" HorizontalAlignment="Left" Margin="93,65,0,0" Name="desc" Text="" VerticalAlignment="Top" Width="357" /> <Button Content="保存" x:Name="saveButton" Click="saveButton_Click" Margin="219,132,6,6" /> </Grid> <ListBox x:Name="toDoItemsListBox" ItemsSource="{Binding EmployeeTables}" Margin="12,241,12,0" Width="440"> <ListBox.ItemTemplate> <DataTemplate> <Grid HorizontalAlignment="Stretch" Width="440"> <Grid.ColumnDefinitions> <ColumnDefinition Width="50" /> <ColumnDefinition Width="*" /> <ColumnDefinition Width="100" /> </Grid.ColumnDefinitions> <TextBlock Text="{Binding EmployeeName}" FontSize="{StaticResource PhoneFontSizeLarge}" Grid.Column="1" VerticalAlignment="Center"/> <Button Grid.Column="2" x:Name="deleteButton" BorderThickness="0" Margin="0" Click="deleteButton_Click" Content="删除"> </Button> <Button Grid.Column="1" x:Name="editButton" BorderThickness="0" Margin="209,0,81,0" Click="editButton_Click" Content="编辑" Grid.ColumnSpan="2"> </Button> </Grid> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Grid>
后台代码：
public partial class MainPage : PhoneApplicationPage { //上下文对象 private EmployeeDataContext employeeDB; //列表集合对象 private EmployeeCollection employeeCollection = new EmployeeCollection(); // Constructor public MainPage() { InitializeComponent(); //连接数据库并初始化DataContext实例 employeeDB = new EmployeeDataContext(EmployeeDataContext.DBConnectionString); //查询所有的记录 var employeeQry = from e in employeeDB.Employees select e; employeeCollection.EmployeeTables=new ObservableCollection<EmployeeTable>(employeeQry); //设置当前页面的上下文对象为列表集合 this.DataContext = employeeCollection; } /// <summary> /// 删除 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void deleteButton_Click(object sender, RoutedEventArgs e) { var button = sender as Button; if (button!=null) { //得到当前按钮所绑定的数据 EmployeeTable employee = button.DataContext as EmployeeTable; //从集合中移除 employeeCollection.EmployeeTables.Remove(employee); //从数据库中移除 employeeDB.Employees.DeleteOnSubmit(employee); //更新到数据库 employeeDB.SubmitChanges(); } } /// <summary> /// 编辑 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void editButton_Click(object sender, RoutedEventArgs e) { var button = sender as Button; if (button!=null) { //得到当前按钮绑定的数据 EmployeeTable employ = button.DataContext as EmployeeTable; //将名称和简介设置为文本框的值 name.Text = employ.EmployeeName; desc.Text = employ.EmployeeDesc; //将当前编辑的对象放置在State中，用于保存时候使用 State["employee"] = employ; //将当前对象从集合中移除 employeeCollection.UpdateEmployee(employ); // employeeCollection.EmployeeTables.Remove(employ); } } /// <summary> /// 保存 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void saveButton_Click(object sender, RoutedEventArgs e) { if (name.Text != "" && desc.Text != "") { //如果当前的State不为空，并且存在Employee，则为编辑 if (State.Count > 0 && State["employee"] != null) { //得到State中的对象 EmployeeTable employ = (EmployeeTable)State["employee"]; //将文本框的值设置给对象 employ.EmployeeName = name.Text; employ.EmployeeDesc = desc.Text; //将数据保存到数据库 employeeDB.SubmitChanges(); // employeeCollection.EmployeeTables.Add(employ); State["employee"] = null; } //新增 else { //创建Employee对象 EmployeeTable employee = new EmployeeTable { EmployeeName = name.Text, EmployeeDesc = desc.Text }; //将Employee放入集合中 employeeCollection.EmployeeTables.Add(employee); //将Employee添加到数据库 employeeDB.Employees.InsertOnSubmit(employee); //将数据更新到数据库 employeeDB.SubmitChanges(); } name.Text = ""; desc.Text = ""; } else { MessageBox.Show("姓名和简介不能为空"); } } }
五、迟到的创建数据库
细心的童鞋会发现，为什么木有创建数据库的过程，如下：
private void Application_Launching(object sender, LaunchingEventArgs e) { using (EmployeeDataContext db=new EmployeeDataContext (EmployeeDataContext.DBConnectionString)) { if (db.DatabaseExists()==false) { db.CreateDatabase(); } } }
在App.xaml.cs中放入上述代码即可，也就是创建了一个数据库。
Tips:数据库文件同样是在独立存储空间中。