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
using System.ComponentModel;
namespace WpfApplicationBindingSample.Models
{
///
/// 业务实体(Business Entity)
///
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
}
}
}
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using System.Windows;
using WpfApplicationBindingSample.Models;
namespace WpfApplicationBindingSample.ViewModels
{
///
/// 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
///
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>
