Windows Phone 7 MVVM模式通讯方式之实现Command

MVVM模式的View与ViewModel的三大通讯方式：Binding Data（实现数据的传递）、Command（实现操作的调用）和Attached Behavior（实现控件加载过程中的操作）。

下面通过一个实例实现MVVM模式的Command通讯

（1）MainPage.xaml文件的代码,实现View层

<phone:PhoneApplicationPage 

x:Class="CommandDemo.MainPage"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"

xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

xmlns:my="clr-namespace:CommandDemo.ViewModel" 

xmlns:my_Interactivity="clr-namespace:CommandDemo.Command" 

xmlns:Custom="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity" xmlns:ic="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions" 

mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"

FontFamily="{StaticResource PhoneFontFamilyNormal}"

FontSize="{StaticResource PhoneFontSizeNormal}"

Foreground="{StaticResource PhoneForegroundBrush}"

SupportedOrientations="Portrait" Orientation="Portrait"

shell:SystemTray.IsVisible="True"> 

<!--设置整个页面的上下文数据DataContext为RadiusViewModel-->

<phone:PhoneApplicationPage.DataContext> 

<my:RadiusViewModel/> 

</phone:PhoneApplicationPage.DataContext> 

<Grid x:Name="LayoutRoot" Background="Transparent"> 

<Grid.RowDefinitions> 

<RowDefinition Height="Auto"/> 

<RowDefinition Height="*"/> 

</Grid.RowDefinitions> 

<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28"> 

<TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/> 

<TextBlock x:Name="PageTitle" Text="Command" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/> 

</StackPanel> 

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"> 

<Ellipse Fill="Red" 

Height="{Binding Radius}" Width="{Binding Radius}" 

HorizontalAlignment="Left" Margin="119,84,0,0" Name="ellipse1" Stroke="Black" StrokeThickness="1" VerticalAlignment="Top" /> 

<Button Content="小" Height="72" HorizontalAlignment="Left" Margin="0,385,0,0" Name="button1" VerticalAlignment="Top" Width="160"> 

<Custom:Interaction.Triggers> 

<Custom:EventTrigger EventName="Click"> 

<my_Interactivity:ExecuteCommandAction CommandName="MinRadius"/> 

</Custom:EventTrigger> 

</Custom:Interaction.Triggers> 

</Button> 

<Button Content="中" Height="72" HorizontalAlignment="Left" Margin="149,384,0,0" Name="button2" VerticalAlignment="Top" Width="160" > 

<Custom:Interaction.Triggers> 

<Custom:EventTrigger EventName="Click"> 

<my_Interactivity:ExecuteCommandAction CommandName="MedRadius"/> 

</Custom:EventTrigger> 

</Custom:Interaction.Triggers> 

</Button> 

<Button Content="大" Height="72" HorizontalAlignment="Left" Margin="299,382,0,0" Name="button3" VerticalAlignment="Top" Width="160" > 

<Custom:Interaction.Triggers> 

<Custom:EventTrigger EventName="Click"> 

<my_Interactivity:ExecuteCommandAction CommandName="MaxRadius"/> 

</Custom:EventTrigger> 

</Custom:Interaction.Triggers> 

</Button> 

</Grid> 

</Grid> 

</phone:PhoneApplicationPage>

（2）RadiusViewModel.cs文件的代码,实现ViewModel层

using System; 

using System.Windows.Input; 

using System.ComponentModel; 

using Microsoft.Expression.Interactivity.Core; 

namespace CommandDemo.ViewModel 

{ 

public class RadiusViewModel : INotifyPropertyChanged 

{ 

private Double radius; 

public RadiusViewModel() 

{ 

Radius = 0; 

MinRadius = new ActionCommand(p => Radius = 100); 

MedRadius = new ActionCommand(p => Radius = 200); 

MaxRadius = new ActionCommand(p => Radius = 300); 

} 

public event PropertyChangedEventHandler PropertyChanged; 

public ICommand MinRadius 

{ 

get; private set; 

} 

public ICommand MedRadius 

{ 

get; 

private set; 

} 

public ICommand MaxRadius 

{ 

get; 

private set; 

} 

public Double Radius 

{ 

get

{ 

return radius; 

} 

set

{ 

radius = value; 

OnPropertyChanged("Radius"); 

} 

} 

protected virtual void OnPropertyChanged(string propertyName) 

{ 

var propertyChanged = PropertyChanged; 

if(propertyChanged != null) 

propertyChanged(this, new PropertyChangedEventArgs(propertyName)); 

} 

} 

}

（3）ExecuteCommandAction.cs类，实现Command操作

using System; 

using System.Windows; 

using System.Windows.Input; 

using System.Windows.Interactivity; 

using System.Reflection; 

namespace CommandDemo.Command 

{ 

public class ExecuteCommandAction : TriggerAction<FrameworkElement> 

{ 

public static readonly DependencyProperty CommandNameProperty = 

DependencyProperty.Register("CommandName", typeof(string), typeof(ExecuteCommandAction), null); 

public static readonly DependencyProperty CommandParameterProperty = 

DependencyProperty.Register("CommandParameter", typeof(object), typeof(ExecuteCommandAction), null); 

protected override void Invoke(object parameter) 

{ 

if (AssociatedObject == null) 

return; 

ICommand command = null; 

var dataContext = AssociatedObject.DataContext; 

foreach (var info in dataContext.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance)) 

{ 

if (IsCommandProperty(info) && String.Equals(info.Name, CommandName, StringComparison.Ordinal)) 

{ 

command = (ICommand)info.GetValue(dataContext, null); 

break; 

} 

} 

if ((command != null) && command.CanExecute(CommandParameter)) 

{ 

command.Execute(CommandParameter); 

} 

} 

private static bool IsCommandProperty(PropertyInfo property) 

{ 

return typeof(ICommand).IsAssignableFrom(property.PropertyType); 

} 

public string CommandName 

{ 

get

{ 

return (string)GetValue(CommandNameProperty); 

} 

set

{ 

SetValue(CommandNameProperty, value); 

} 

} 

public object CommandParameter 

{ 

get

{ 

return GetValue(CommandParameterProperty); 

} 

set

{ 

SetValue(CommandParameterProperty, value); 

} 

} 

} 

}