原文:在WPF应用程序中利用IEditableObject接口实现可撤销编辑的对象
这是我辅导的一个项目开发中的例子，他们是用WPF做界面开发，在学习了如何使用MVVM来实现界面与逻辑的分离，并且很好的数据更新之后，有一个疑问就是，这种双向的数据更新确实很不错，但如果我们希望用户可以撤销修改怎么办呢？其实这个功能，很早就有，甚至在原先的Windows Forms里面也可以实现。秘密就是实现IEditableObject这个接口。
关于这个接口的官方文档在这里：http://msdn.microsoft.com/zh-cn/library/vstudio/system.componentmodel.ieditableobject.aspx
我做了一个小的例子，帮助大家来理解。该例子使用了MVVM这种设计模式，如果你对此不熟悉，请先参考：http://www.cnblogs.com/chenxizhang/archive/2011/10/01/2197786.html
这个例子，你可以通过 http://files.cnblogs.com/chenxizhang/WpfApplicationBindingSample.zip 进行下载
Model：Employee
using System.ComponentModel; namespace WpfApplicationBindingSample.Models { /// <summary> /// 业务实体(Business Entity) /// </summary> class Employee : INotifyPropertyChanged,IEditableObject { private string _firstName; public string FirstName { get { return _firstName; } set { if (_firstName != value) { _firstName = value; if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("FirstName")); PropertyChanged(this, new PropertyChangedEventArgs("FullName")); } } } } private string _lastName; public string LastName { get { return _lastName; } set { if (_lastName != value) { _lastName = value; if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("LastName")); PropertyChanged(this, new PropertyChangedEventArgs("FullName")); } } } } public string FullName { get { return FirstName + "," + LastName; } } public event PropertyChangedEventHandler PropertyChanged; private Employee backup;//用这个字段来保存一个备份数据 public void BeginEdit() { //开始编辑，此时将当前的状态保存起来，以便后续可以根据情况提交或者撤销更改 backup = this.MemberwiseClone() as Employee;//通过克隆的方式直接地复制一份数据 } public void CancelEdit() { //撤销编辑，此时将对象状态恢复到备份的状态 this.FirstName = backup.FirstName; this.LastName = backup.LastName; } public void EndEdit() { //结束编辑，这里可以不做任何事情，也可以添加一些额外的逻辑 } } }
ViewModel:
using GalaSoft.MvvmLight; using GalaSoft.MvvmLight.Command; using System.Windows; using WpfApplicationBindingSample.Models; namespace WpfApplicationBindingSample.ViewModels { /// <summary> /// 视图模型：专门用来为界面（视图）来服务的，这里用来包含一些业务逻辑 /// </summary> class MainWindowViewModel : ViewModelBase { public MainWindowViewModel() { CurrentEmployee = new Employee() { FirstName = "ares", LastName = "chen" }; } public Employee CurrentEmployee { get; set; } public RelayCommand EditCommand { get { return new RelayCommand(() => { //将该员工设置为开始编辑 CurrentEmployee.BeginEdit(); }); } } /// <summary> /// 使用命令的机制代替了事件 /// </summary> public RelayCommand SubmitCommand { get {//使用匿名方法 return new RelayCommand(() => { //结束编辑，让更改生效 CurrentEmployee.EndEdit(); MessageBox.Show(CurrentEmployee.FullName); }); } } public RelayCommand CancelCommand { get { return new RelayCommand(() => { CurrentEmployee.CancelEdit();//取消编辑，此时可以看到FullName那个标签的文本恢复到原来的值 }); } } } }
View:
<Window x:Class="WpfApplicationBindingSample.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:vm="clr-namespace:WpfApplicationBindingSample.ViewModels" Title="MainWindow" Height="350" Width="525"> <Window.DataContext> <!--绑定数据上下文--> <vm:MainWindowViewModel></vm:MainWindowViewModel> </Window.DataContext> <Window.Resources> <Style TargetType="TextBlock"> <Setter Property="Margin" Value="3"></Setter> </Style> <Style TargetType="TextBox"> <Setter Property="Width" Value="200"></Setter> <Setter Property="HorizontalAlignment" Value="Left"></Setter> </Style> <Style TargetType="Button"> <Setter Property="Width" Value="100"></Setter> <Setter Property="HorizontalAlignment" Value="Left"></Setter> </Style> </Window.Resources> <StackPanel Margin="10"> <TextBlock FontSize="30" Text="编辑员工"></TextBlock> <TextBlock Text="姓氏"></TextBlock> <TextBox Text="{Binding CurrentEmployee.FirstName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"></TextBox> <!--匈牙利命名法--> <TextBlock Text="名称"></TextBlock> <TextBox Text="{Binding CurrentEmployee.LastName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"></TextBox> <TextBlock Text="全称"></TextBlock> <TextBlock Text="{Binding CurrentEmployee.FullName}"></TextBlock> <Button Content="编辑" Command="{Binding EditCommand}"></Button> <Button Content="提交" Command="{Binding SubmitCommand}"></Button> <Button Content="取消" Command="{Binding CancelCommand}"></Button> </StackPanel> </Window>
