Windows Phone 7 MVVM模式通訊方式之實現Command

MVVM模式的View與ViewModel的三大通訊方式：Binding Data（實現資料的傳遞）、Command（實現操作的調用）和Attached Behavior（實現控制項載入過程中的操作）。(1)Windows Phone 7 MVVM模式通訊方式之實現Binding Data。(2)Windows Phone 7 MVVM模式通訊方式之實現Command。(3)Windows Phone 7 MVVM模式通訊方式之實現Attached Behavior。下面通過一個執行個體實現MVVM模式的Command通訊（1）MainPage.xaml檔案的代碼,實現View層

<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">    <!--設定整個頁面的上下文資料DataContext為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檔案的代碼,實現ViewModel層

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類，實現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);            }        }    }}