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。