EventToCommand

在WPF中，并不是所有控件都有Command，例如TextBox，那么当文本改变，我们需要处理一些逻辑，这些逻辑在ViewModel

中，没有Command如何绑定呢？这个时候我们就用到EventToCommand，事件转命令，可以将一些事件例如TextChanged，Checked等

转换成命令的方式。

不带参数的EventToCommand

AppView.xaml

       <CheckBox>

            <i:Interaction.Triggers>

                <i:EventTrigger EventName="Checked">

                    <command:EventToCommand Command="{Binding CheckedCommand}"></command:EventToCommand>

                </i:EventTrigger>

                <i:EventTrigger EventName="Unchecked">

                    <command:EventToCommand Command="{Binding UnCheckedCommand}"></command:EventToCommand>

                </i:EventTrigger>

            </i:Interaction.Triggers>

        </CheckBox>

AppViewModel.cs

        public RelayCommand CheckedCommand

        {

            get;

            set;

        }

        public RelayCommand UnCheckedCommand

        {

            get;

            set;

        }

        public AppViewModel()

        {

            CheckedCommand = new RelayCommand(Checked);

            UnCheckedCommand = new RelayCommand(UnChecked);

        }

        private void Checked()

        {

            MessageBox.Show("Checked");

        }

        private void UnChecked()

        {

            MessageBox.Show("Unchecked");

        }

带参数的EventToCommand

AppView.xaml

        <Button Width="100" Height="30" Margin="0,100,0,0">

            <i:Interaction.Triggers>

                <i:EventTrigger EventName="Click">

                    <command:EventToCommand Command="{Binding ShowTxtCommand}" PassEventArgsToCommand="True" CommandParameter="Hello"></command:EventToCommand>

                </i:EventTrigger>

            </i:Interaction.Triggers>

        </Button>

AppViewModel.cs

        /// <summary>

        /// 显示消息命令

        /// </summary>

        public RelayCommand<string> ShowTxtCommand

        {

            get;

            set;

        }

        public AppViewModel()

        {

            ShowTxtCommand=new RelayCommand<string>(ShowMsg);

        }

        /// <summary>

        /// 命令具体实现

        /// </summary>

        private void ShowMsg(string msg)

        {

            MessageBox.Show(msg);

        }

转换传递的参数

也许你想知道事件是谁触发的，从而进行一些业务逻辑，那么我们需要从IEventArgsConverter继承

EventArgsConverter.cs

public class EventArgsConverter : IEventArgsConverter

{

    public object Convert(object value, object parameter)

    {

        var args = (RoutedEventArgs)value;

        var btn = parameter as Button;

        return btn.Name;

    }

}

AppView.xaml

   <Button Width="100" Height="30" Margin="0,100,0,0" x:Name="btn">

        <i:Interaction.Triggers>

            <i:EventTrigger EventName="Click">

                <command:EventToCommand Command="{Binding ShowNameCommand}" EventArgsConverter="{StaticResource ArgsConverter}" EventArgsConverterParameter="{Binding ElementName=btn}" PassEventArgsToCommand="True"></command:EventToCommand>

            </i:EventTrigger>

        </i:Interaction.Triggers>

    </Button>

AppViewModel.cs

    public RelayCommand<string> ShowNameCommand

    {

        get;

        set;

    }

    public AppViewModel()

    {

        ShowNameCommand = new RelayCommand<string>(ShowName);

    }

    private void ShowName(string name)

    {

        MessageBox.Show(name);

    }

看了EventToCommand的源码，并没有什么帮助，我猜测它的实现是这样的，EventToCommand属于附加

属性，它就能获取到它所附加的对象即控件本身，然后它还能Binding命令，比如我们附加的对象是Button

，那么就在它的Click事件时，触发Command命令，同样，有条件判断Command是否能执行时，可以设置

控件的IsEnabled属性。