创建使用本地数据库的WP7应用程序-优快云博客

本文介绍了如何在WP7应用中创建并使用本地数据库，包括定义数据上下文、创建数据表实体类、初始化数据库、实现数据绑定以及添加、删除数据操作。通过示例展示了如何处理TodoItem数据模型，并提供了数据保存和加载的方法。

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wp7支持本地数据库了，如下是创建使用本地数据库应用程序的基本方法：

第一步：构建数据上下文

添加引用：System.Data.Linq，并在程序中要用到的地方添加如下代码：

using System.Data.Linq;
using System.Data.Linq.Mapping;
using System.ComponentModel;
using System.Collections.ObjectModel;

添加数据表实体类：

[Table]
public class ToDoItem : INotifyPropertyChanged, INotifyPropertyChanging
{
// Define ID: private field, public property and database column.
private int _toDoItemId;

[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int ToDoItemId
{
    get
    {
        return _toDoItemId;
    }
    set
    {
        if (_toDoItemId != value)
        {
            NotifyPropertyChanging("ToDoItemId");
            _toDoItemId = value;
            NotifyPropertyChanged("ToDoItemId");
        }
    }
}

// Define item name: private field, public property and database column.
private string _itemName;

[Column]
public string ItemName
{
    get
    {
        return _itemName;
    }
    set
    {
        if (_itemName != value)
        {
            NotifyPropertyChanging("ItemName");
            _itemName = value;
            NotifyPropertyChanged("ItemName");
        }
    }
}

// Define completion value: private field, public property and database column.
private bool _isComplete;

[Column]
public bool IsComplete
{
    get
    {
        return _isComplete;
    }
    set
    {
        if (_isComplete != value)
        {
            NotifyPropertyChanging("IsComplete");
            _isComplete = value;
            NotifyPropertyChanged("IsComplete");
        }
    }
}
// Version column aids update performance.
[Column(IsVersion = true)]
private Binary _version;

#region INotifyPropertyChanged Members

public event PropertyChangedEventHandler PropertyChanged;

// Used to notify the page that a data context property changed
private void NotifyPropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

#endregion

#region INotifyPropertyChanging Members

public event PropertyChangingEventHandler PropertyChanging;

// Used to notify the data context that a data context property is about to change
private void NotifyPropertyChanging(string propertyName)
{
    if (PropertyChanging != null)
    {
        PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
    }
}

#endregion
}

数据上下文类：

public class ToDoDataContext : DataContext
{
    // Specify the connection string as a static, used in main page and app.xaml.
    public static string DBConnectionString = "Data Source=isostore:/ToDo.sdf";

    // Pass the connection string to the base class.
    public ToDoDataContext(string connectionString)
        : base(connectionString)
    { }

    // Specify a single table for the to-do items.
    public Table<ToDoItem> ToDoItems;
}

第二部：创建数据库

在App类构造函数末尾添加代码，如果数据库不存在则创建：

// Create the database if it does not exist.
using (ToDoDataContext db = new ToDoDataContext(ToDoDataContext.DBConnectionString))
{
    if (db.DatabaseExists() == false)
    {
        //Create the database
        db.CreateDatabase();
    }
}

为了支持数据绑定，使相应的类实现INotifyPropertyChanged接口：

public partial class MainPage : PhoneApplicationPage, INotifyPropertyChanged
{

    // Constructor
    public MainPage()
    {
        InitializeComponent();
    }


    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    // Used to notify Silverlight that a property has changed.
    private void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion
}

在相应类构造函数里声明一个DataContext，如下代码：

// Data context for the local database
private ToDoDataContext toDoDB;

// Define an observable collection property that controls can bind to.
private ObservableCollection<ToDoItem> _toDoItems;
public ObservableCollection<ToDoItem> ToDoItems
{
    get
    {
        return _toDoItems;
    }
    set
    {
        if (_toDoItems != value)
        {
            _toDoItems = value;
            NotifyPropertyChanged("ToDoItems");
        }
    }
}

在构造函数末尾添加如下代码：

// Connect to the database and instantiate data context.
toDoDB = new ToDoDataContext(ToDoDataContext.DBConnectionString);
            
// Data context and observable collection are children of the main page.
this.DataContext = this;

重写函数在页面加载前从数据库获取信息：protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
// Define the query to gather all of the to-do items.
var toDoItemsInDB = from ToDoItem todo in toDoDB.ToDoItems
                    select todo;

// Execute the query and place the results into a collection.
ToDoItems = new ObservableCollection<ToDoItem>(toDoItemsInDB);
            
    // Call the base method.
    base.OnNavigatedTo(e);
}

重写函数以便在页面变成非活动状态时做数据的保存工作： protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
{
    // Call the base method.
    base.OnNavigatedFrom(e);

    // Save changes to the database.
    toDoDB.SubmitChanges();
}

数据添加：private void newToDoAddButton_Click(object sender, RoutedEventArgs e)
{
    // Create a new to-do item based on the text box.
    ToDoItem newToDo = new ToDoItem { ItemName = newToDoTextBox.Text };

    // Add a to-do item to the observable collection.
    ToDoItems.Add(newToDo);
            
    // Add a to-do item to the local database.
    toDoDB.ToDoItems.InsertOnSubmit(newToDo);          
}

数据删除：private void deleteTaskButton_Click(object sender, RoutedEventArgs e)
{
    // Cast parameter as a button.
    var button = sender as Button;

    if (button != null)
    {
        // Get a handle for the to-do item bound to the button.
        ToDoItem toDoForDelete = button.DataContext as ToDoItem;

        // Remove the to-do item from the observable collection.
        ToDoItems.Remove(toDoForDelete);

        // Remove the to-do item from the local database.
        toDoDB.ToDoItems.DeleteOnSubmit(toDoForDelete);

        // Save changes to the database.
        toDoDB.SubmitChanges();

        // Put the focus back to the main page.
        this.Focus();
    }
}

注：以上代码来自网络，使用时需理解后灵活变通