WPF - Command

在 XAML 中

1，创建一个command对象，可以直接使用RoutedCommand,然后通过CommandBinding来指定Execute和CanExecute；

2，指定 Command 。例子中使用的是CheckBox, 实际上Command是ButtonBase的成员，所以，所有ButtonBase的派生类都适用该方法，如RadioButton, RepeatButton,等等。

Command 是一个 StaticResource

<Window
    x:Class="Program.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Window.Resources>
        <RoutedCommand x:Key="MyCmd"/>
    </Window.Resources>
    <Window.CommandBindings>
        <CommandBinding Command="{StaticResource MyCmd}" CanExecute="MyCmd_CanExecute" Executed="MyCmd_Executed"/>
     </Window.CommandBindings>
    <Grid>
        <CheckBox Command="{StaticResource MyCmd}"
                  CommandParameter="{Binding IsChecked, RelativeSource={RelativeSource Self}}"
                  Content="I have been binded to a command"/>
    </Grid>
</Window>

 

使用 M-V-VM 模式

可以在你的Model或者View Model中提供一个ICommand的Property被Binding. 注意，上面的方法中是StaticResource，这里是Binding

 

namespace Program
{
    public class Model : INotifyPropertyChanged
    {
        #region implement interface INotifyPropertyChanged
        public event PropertyChangedEventHandler PropertyChanged;
        protected void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }
        #endregion

        private RelayCommand _myCmd = null;
        public ICommand MyCmd
        {
            get
            {
                if(_myCmd==null)
                    _myCmd = new RelayCommand(param => MyCmdExecute(param));
                return _myCmd;
            }
        }

        private void MyCmdExecute(object param)
        {
            MessageBox.Show(param.ToString());
        }
    }
}

 

<Window
    x:Class="Program.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300"
    >
    <Grid>
        <Button Command="{Binding MyCmd}" CommandParameter="hello!" Content="I have been bound to a command" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Grid>
</Window>

 

namespace Program
{
    public class RelayCommand : ICommand
    {
        #region ICommand realization

        [DebuggerStepThrough]
        public bool CanExecute(object parameter)
        {
            return _canExecute == null ? true : _canExecute(parameter);
        }

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public void Execute(object parameter)
        {
            _execute(parameter);
        }

        #endregion

        readonly Action<object> _execute;
        readonly Predicate<object> _canExecute;

        public RelayCommand(Action<object> execute)
            : this(execute, null)
        { }

        public RelayCommand(Action<object> execute, Predicate<object> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("RelayCommand argument can not be null!");

            _execute = execute;
            _canExecute = canExecute;
        }
    }
}

 

namespace Program
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        private Model Dat = new Model();

        public Window1()
        {
            this.DataContext = Dat;
            InitializeComponent();
        }
    }
}