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）。

(1)Windows Phone 7 MVVM模式通讯方式之实现Binding Data。

(2)Windows Phone 7 MVVM模式通讯方式之实现Command。

(3)Windows Phone 7 MVVM模式通讯方式之实现Attached Behavior。

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

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<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

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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

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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);

}

}

}

}