MVVM 的事件处理： 利用Prism框架进行EventToCommand

Prism框架只对Button提供了Command的附加属性，虽然通过ControlTemplate可以实现大部分的功能，但是总是重写ControlTemplate未免费时费力，而且重写的ControlTemplate还不一定有原来的动态效果，这里提供一个解决方案。

此处对ComboBox的SelectionChanged事件做EventToCommand。

这里用到Prism中的CommandBehaviorBase类。

1. 定义附加属性类SelectedChanged.cs

 public class SelectedChanged

    {

        private static readonly DependencyProperty SelectedChangedCommandBehaviorProperty = DependencyProperty.RegisterAttached(

          "SelectedChangedCommandBehavior",

          typeof(ComboBoxSelectChangedCommandBehavior),

          typeof(SelectedChanged),

          null);



        public static readonly DependencyProperty CommandProperty = DependencyProperty.RegisterAttached(

            "Command",

            typeof(ICommand),

            typeof(SelectedChanged),

            new PropertyMetadata(OnSetCommandCallback));



        public static readonly DependencyProperty CommandParameterProperty = DependencyProperty.RegisterAttached(

            "CommandParameter",

            typeof(object),

            typeof(SelectedChanged),

            new PropertyMetadata(OnSetCommandParameterCallback));





        public static void SetCommand(ComboBox CBox, ICommand command)

        {

            if (CBox == null) throw new System.ArgumentNullException("CBox");

            CBox.SetValue(CommandProperty, command);

        }



        public static ICommand GetCommand(ComboBox CBox)

        {

            if (CBox == null) throw new System.ArgumentNullException("CBox");

            return CBox.GetValue(CommandProperty) as ICommand;

        }



        public static void SetCommandParameter(ComboBox CBox, object parameter)

        {

            if (CBox == null) throw new System.ArgumentNullException("CBox");

            CBox.SetValue(CommandParameterProperty, parameter);

        }



        public static object GetCommandParameter(ComboBox CBox)

        {

            if (CBox == null) throw new System.ArgumentNullException("CBox");

            return CBox.GetValue(CommandParameterProperty);

        }



        private static void OnSetCommandCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)

        {

            ComboBox CBox = dependencyObject as ComboBox;

            if (CBox != null)

            {

                ComboBoxSelectChangedCommandBehavior behavior = GetOrCreateBehavior(CBox);

                behavior.Command = e.NewValue as ICommand;

            }

        }



        private static void OnSetCommandParameterCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)

        {

            ComboBox CBox = dependencyObject as ComboBox;

            if (CBox != null)

            {

                ComboBoxSelectChangedCommandBehavior behavior = GetOrCreateBehavior(CBox);

                behavior.CommandParameter = e.NewValue;

            }

        }



        private static ComboBoxSelectChangedCommandBehavior GetOrCreateBehavior(ComboBox CBox)

        {

            ComboBoxSelectChangedCommandBehavior behavior = CBox.GetValue(SelectedChangedCommandBehaviorProperty) as ComboBoxSelectChangedCommandBehavior;

            if (behavior == null)

            {

                behavior = new ComboBoxSelectChangedCommandBehavior(CBox);

                CBox.SetValue(SelectedChangedCommandBehaviorProperty, behavior);

            }



            return behavior;

        }

    }

2. 定义Behavior类

  public ComboBoxSelectChangedCommandBehavior(ComboBox CMBObject)

            : base(CMBObject)

        {

            if (CMBObject == null) throw new System.ArgumentNullException("CMBObject can't be null");

            CMBObject.SelectionChanged += (s, e) =>

            {

                ExecuteCommand();

            };

        }

 OK！接下来在ComboBox就可以使用这个附加属性了

 Lcommands:SelectedChanged.Command="{Binding FamilySelectCommand}"  
 Lcommands:SelectedChanged.CommandParameter="{Binding SelectedItem, RelativeSource={RelativeSource Self}}"/>