这是上一篇“Silverlight：双向绑定综合应用-自动更新集合汇总字段”的续篇。需求场景如下：
一个公司，有N个员工，逢年过节时要搞一些抽奖活动，最终要公告收奖名单。
"员工"类如下：
namespace CollectionBinding
{
/// <summary>
/// 员工类
/// </summary>
public class Employee : NotifyPropertyChangedObject
{
private string _name = "";
public string Name
{
set
{
_name = value;
OnPropertyChanged("Name");
}
get
{
return _name;
}
}
private int _salary = 0;
public int Salary
{
get
{
return _salary;
}
set
{
_salary = value;
OnPropertyChanged("Salary");
}
}
}
}
“员工中奖记录”类如下：
namespace CollectionBinding
{
/// <summary>
/// 员工中奖记录
/// </summary>
public class EmployeePrize : NotifyPropertyChangedObject
{
private string _employeeName = "";
/// <summary>
/// 中奖员工的名字
/// </summary>
public string EmployeeName
{
get { return _employeeName; }
set { _employeeName = value; OnPropertyChanged("EmployeeName"); }
}
private string _prizeName = "";
/// <summary>
/// 奖品名称
/// </summary>
public string PrizeName
{
get { return _prizeName; }
set { _prizeName = value; OnPropertyChanged("PrizeName"); }
}
}
}
NotifyPropertyChangedObject是一个基类
using System.ComponentModel;
namespace CollectionBinding
{
public class NotifyPropertyChangedObject : INotifyPropertyChanged
{
public NotifyPropertyChangedObject()
{
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
录入中奖员工时，要求“员工的名字”必须从公司的员工中选取，如果发现某位员工在公司的员工库里没有登记，也可以在这个界面上的员工列表中临时添加。
界面原型如下：
即：下面网格中的员工“姓名下拉框”数据来源，依赖于上面网格中的员工姓名记录。（类似数据库中的主从表关系）
为了实现这种绑定，需要创建二个ViewModel类
EmployeePrizeViewModel类，用来实现下面一个网格的绑定，代码如下:
using System.ComponentModel;
using System.Collections.ObjectModel;
namespace CollectionBinding
{
public class EmployeePrizeViewModel : NotifyPropertyChangedObject
{
private ObservableCollection<Employee> _employees = new ObservableCollection<Employee>();
public ObservableCollection<Employee> Employees
{
get { return _employees; }
set { _employees = value; OnPropertyChanged("Employees"); }
}
private EmployeePrize _employeePrize = new EmployeePrize();
public EmployeePrize EmployeePrize
{
get { return _employeePrize; }
set { _employeePrize = value; OnPropertyChanged("EmployeePrize"); }
}
}
}
上面的网格绑定，用CompanyViewModel来实现
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Text;
using System.Xml.Serialization;
namespace CollectionBinding
{
public class CompanyViewModel : NotifyPropertyChangedObject
{
private ObservableCollection<Employee> _employeeCollection = new ObservableCollection<Employee>();
/// <summary>
/// 公司的"员工集合"
/// </summary>
public ObservableCollection<Employee> EmployeeCollection
{
get { return _employeeCollection; }
}
private ObservableCollection<EmployeePrizeViewModel> _employeePrizeViewModelCollection = new ObservableCollection<EmployeePrizeViewModel>();
/// <summary>
/// 中奖名单
/// </summary>
public ObservableCollection<EmployeePrizeViewModel> EmployeePrizeViewModelCollection
{
get { return _employeePrizeViewModelCollection; }
}
/// <summary>
/// 构造函数
/// </summary>
public CompanyViewModel()
{
_employeeCollection.CollectionChanged += new NotifyCollectionChangedEventHandler(_employeeCollection_CollectionChanged);
}
/// <summary>
/// 员工有“增减”时自动触发
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void _employeeCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
//重新计算工资总和
computeSalaryTotal();
//每个员工的“工资”属性变化时，自动触发指定事件
foreach (var item in _employeeCollection)
{
item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
}
}
/// <summary>
/// 员工属性变化时自动调用本方法
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
//如果是"工资"属性变化，则自动重新计算工资汇总
if (e.PropertyName == "Salary")
{
computeSalaryTotal();
}
}
private void computeSalaryTotal()
{
_salaryTotal = _employeeCollection.Sum(c => c.Salary);
OnPropertyChanged("SalaryTotal");//工资总合重新计算后，向外广播事件，以便UI能自动更新
}
private int _salaryTotal = 0;
/// <summary>
/// 工资汇总
/// </summary>
public int SalaryTotal
{
get
{
return _salaryTotal;
}
}
public override string ToString()
{
string result = "";
XmlSerializer xmlSerializer = new XmlSerializer(typeof(CompanyViewModel));
using (MemoryStream ms = new MemoryStream())
{
try
{
xmlSerializer.Serialize(ms, this);
result = Encoding.UTF8.GetString(ms.ToArray(), 0, (int)ms.Length);
}
catch { }
}
return result;
}
}
}
类图：
最终界面的Xaml代码:
<UserControl x:Class="CollectionBinding.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400" xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">
<StackPanel x:Name="LayoutRoot" Background="White">
<sdk:DataGrid AutoGenerateColumns="False" HorizontalAlignment="Center" Margin="0,10,0,0" Name="dataGrid1" VerticalAlignment="Center" ItemsSource="{Binding EmployeeCollection,Mode=TwoWay}">
<sdk:DataGrid.Columns>
<sdk:DataGridTemplateColumn Header="姓名" Width="100">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBox Text="{Binding Name,Mode=TwoWay}" VerticalAlignment="Center" Margin="1"></TextBox>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
<sdk:DataGridTemplateColumn Header="工资" Width="100">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBox Text="{Binding Salary,Mode=TwoWay}" VerticalAlignment="Center" Margin="1"></TextBox>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
<sdk:DataGridTemplateColumn Header="操作">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Button Click="RemoveEmployee" HorizontalAlignment="Center" VerticalAlignment="Center" Padding="10,1">-</Button>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
</sdk:DataGrid.Columns>
</sdk:DataGrid>
<StackPanel HorizontalAlignment="Center" Orientation="Horizontal" Margin="5">
<TextBlock VerticalAlignment="Center">工资总合：</TextBlock>
<TextBlock Text="{Binding SalaryTotal, Mode=TwoWay}" Margin="5,0,5,0" Width="60"></TextBlock>
</StackPanel>
<Button Click="AddEmployee" Padding="10,1" Margin="5" HorizontalAlignment="Center">+</Button>
<Border BorderBrush="Black" BorderThickness="0,1,0,0" Width="300"></Border>
<sdk:DataGrid AutoGenerateColumns="False" HorizontalAlignment="Center" Margin="0,10,0,0" Name="dataGrid2" VerticalAlignment="Center" ItemsSource="{Binding EmployeePrizeViewModelCollection,Mode=TwoWay}">
<sdk:DataGrid.Columns>
<sdk:DataGridTemplateColumn Header="姓名" Width="100">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Employees,Mode=TwoWay}" SelectedValuePath="Name" SelectedValue="{Binding EmployeePrize.EmployeeName,Mode=TwoWay}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}"></TextBlock>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
<sdk:DataGridTemplateColumn Header="奖品" Width="100">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBox Text="{Binding EmployeePrize.PrizeName,Mode=TwoWay}" VerticalAlignment="Center" Margin="1"></TextBox>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
<sdk:DataGridTemplateColumn Header="操作">
<sdk:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Button Click="RemoveEmployeePrize" HorizontalAlignment="Center" VerticalAlignment="Center" Padding="10,1">-</Button>
</DataTemplate>
</sdk:DataGridTemplateColumn.CellTemplate>
</sdk:DataGridTemplateColumn>
</sdk:DataGrid.Columns>
</sdk:DataGrid>
<Button Click="AddEmployeePrize" Padding="10,1" Margin="5" HorizontalAlignment="Center">+</Button>
<Button HorizontalAlignment="Center" Padding="10,2" Click="ShowCompanyViewModel">查看CompanyViewModel内容</Button>
<TextBox Name="textBox1" Margin="5" Height="200" TextWrapping="Wrap" ScrollViewer.VerticalScrollBarVisibility="Visible"/>
</StackPanel>
</UserControl>
后面Xaml.cs 部分:
using System.Windows;
using System.Windows.Controls;
namespace CollectionBinding
{
public partial class MainPage : UserControl
{
CompanyViewModel c = new CompanyViewModel();
public MainPage()
{
InitializeComponent();
this.Loaded += new RoutedEventHandler(MainPage_Loaded);
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
//伪造一些数据，测试绑定
Employee e1 = new Employee() { Name = "张三", Salary = 3000 };
Employee e2 = new Employee() { Name = "李四", Salary = 4000 };
Employee e3 = new Employee() { Name = "杨过", Salary = 9999 };
c.EmployeeCollection.Add(e1);
c.EmployeeCollection.Add(e2);
c.EmployeeCollection.Add(e3);
EmployeePrizeViewModel p1 = new EmployeePrizeViewModel() { Employees = c.EmployeeCollection, EmployeePrize = new EmployeePrize() { EmployeeName = "杨过", PrizeName = "玄铁剑" } };
EmployeePrizeViewModel p2 = new EmployeePrizeViewModel() { Employees = c.EmployeeCollection, EmployeePrize = new EmployeePrize() { EmployeeName = "李四", PrizeName = "ThinkPad X220" } };
c.EmployeePrizeViewModelCollection.Add(p1);
c.EmployeePrizeViewModelCollection.Add(p2);
this.DataContext = c;
}
/// <summary>
/// 删除员工
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void RemoveEmployee(object sender, RoutedEventArgs e)
{
var emp = (sender as Button).DataContext as Employee;
if (emp != null) { c.EmployeeCollection.Remove(emp); }
}
/// <summary>
/// 添加员工
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void AddEmployee(object sender, RoutedEventArgs e)
{
c.EmployeeCollection.Add(new Employee() { Name = "新人", Salary = 1000 });
}
/// <summary>
/// 增加中奖名单
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void AddEmployeePrize(object sender, RoutedEventArgs e)
{
var empPrizeViewModel = new EmployeePrizeViewModel() { Employees = c.EmployeeCollection };
var empPrize = new EmployeePrize();
if (c.EmployeeCollection.Count > 0)
{
empPrize.EmployeeName = c.EmployeeCollection[c.EmployeeCollection.Count - 1].Name;
}
empPrizeViewModel.EmployeePrize = empPrize;
c.EmployeePrizeViewModelCollection.Add(empPrizeViewModel);
}
/// <summary>
/// 删除中奖名单
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void RemoveEmployeePrize(object sender, RoutedEventArgs e)
{
var empPrizeViewModel = (sender as Button).DataContext as EmployeePrizeViewModel;
if (empPrizeViewModel != null) { c.EmployeePrizeViewModelCollection.Remove(empPrizeViewModel); }
}
private void ShowCompanyViewModel(object sender, RoutedEventArgs e)
{
this.textBox1.Text = c.ToString();
}
}
}
作者：菩提树下的杨过
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