参考:http://caliburn.codeplex.com/wikipage?title=Command%20Basics&referringTitle=Documentation

command在wpf的viewmodel中使用的非常的广泛,讨论的也非常多.

来看下caliburn对command的支持

caliburn支持三种方式command的注册

• 容器
• 资源
• 绑定

Command解析字符串

parser.RegisterMessageParser("ResourceCommand", new CommandMessageParser(binder, CommandSource.Resource));
parser.RegisterMessageParser("ContainerCommand", new CommandMessageParser(binder, CommandSource.Container));
parser.RegisterMessageParser("BoundCommand", new CommandMessageParser(binder, CommandSource.Bound));

为简化xaml,在Attach中采用了特定解析的字符串,下面可以看到

1.使用容器

首先定义一个对象

注意点:

1. 挂上Command标签
2. 方法必须为Execute和CanExecute

[Command]
public class ShowMessageCommand
{//Note: A command must have an entry point.  A method named 'Execute' is searched for by default.  //Note: Use the CommandAttribute.ExecuteMethod to specify a different method.//Note: The 'Execute' method inherits all the features available to actions.public void Execute(string message){MessageBox.Show(message);}//NOTE:  This is picked up automatically by the ActionFactory based on its naming convention.public bool CanExecute(string message){return !string.IsNullOrEmpty(message);}
}

xaml

<Button Content="Attached Container Command w/ 1 Parameter" cal:Message.Attach="ContainerCommand ShowMessage(message.Text)"/>

注意xaml使用方式,ContainerCommand为特定的解析字符串ShowMessage则代表ShowMessageCommand,以下规则是一样的

2.使用资源

首先然后定义对象,注意Preview标签

public class ShowTitledMessageCommand
{//Note: A command must have a method named 'Execute'//Note: The 'Execute' method inherits all the features available to actions.[Preview("CanExecute")]public void Execute(string title, string message){MessageBox.Show(message, title);}public bool CanExecute(string title, string message){return !string.IsNullOrEmpty(title) && !string.IsNullOrEmpty(message);}
}

定义资源

<Window.Resources><!--Note: Adding a command to resources.--><local:ShowTitledMessageCommand x:Key="ShowTitledMessage" />
</Window.Resources>

xaml引用

<Button Content="Attached Resource Command w/ 2 Parameters"cal:Message.Attach="ResourceCommand ShowTitledMessage(title.Text, message.Text)" />

3.使用绑定

要绑定的前提是需要有源

首先要定义源

<Window.DataContext><!--Note: Makes the presentation model available for binding through the data context.--><local:MyModel />
</Window.DataContext>

使用BoundCommand绑定

<TextBox x:Name="message" /><!--Note: Executes the command located through data binding.  The framework infers the trigger type.-->
<Button Content="Click Me!"cal:Message.Attach="BoundCommand TheCommand(message.Text)" />

我们通过代码来看下不同的解析过程

        protected override void SetCore(CommandMessage message, DependencyObject target, string coreOfMessage){switch(_commandSource){case CommandSource.Resource:var frameworkElement = target as FrameworkElement;if(frameworkElement != null){frameworkElement.Loaded +=delegate { message.Command = frameworkElement.GetResource<object>(coreOfMessage); };}
                    break;case CommandSource.Container:message.Command = ServiceLocator.Current.GetInstance(null, coreOfMessage);break;case CommandSource.Bound:var binding = new Binding(coreOfMessage);BindingOperations.SetBinding(message, CommandMessage.CommandProperty, binding);
                    break;default:throw new NotSupportedException(_commandSource + " is not a supported command source.");}}

实质上是非常简单的,主要手段还是通过给CommandMessage的Command赋值,方式不同而已.以上三种方式一比较，第一种是最简单的,这也是依赖注入带来的好处,不需要事先显示声明对象.效果都是一样的

来看下原始的用法

<Button Content="Triggers: Container Command With 1 Explicit Parameters"><cal:Message.Triggers><cal:RoutedMessageTriggerCollection><cal:EventMessageTrigger EventName="Click"><cal:EventMessageTrigger.Message><!--Note ResolveExtension doesn't exist in Silverlight, but you can auto resolve by string key. See SL samples.--><cal:CommandMessage Command="{cal:Resolve Key=ShowMessage}"><!--Note: The declaration of parameters is different from Silverlight.--><cal:Parameter Value="{Binding ElementName=message, Path=Text}"/></cal:CommandMessage></cal:EventMessageTrigger.Message></cal:EventMessageTrigger></cal:RoutedMessageTriggerCollection></cal:Message.Triggers>
</Button>