WPF实现支持Command绑定的ComboBox控件
<div id="cnblogs_post_body">由于ComboBox，ListBox等控件没有实现ICommandSource接口，所以不支持在XAML中进行Command绑定，下面的一段代码就是，对ComboBox实现对ICommandSource接口的实现：<div class="cnblogs_code" style="background-color: #f5f5f5; border: #cccccc 1px solid; padding: 5px;">public class ComboBoxWithCommand : ComboBox, ICommandSource{ private static EventHandler canExecuteChangedHandler; public static readonly DependencyProperty CommandProperty = DependencyProperty.Register("Command", typeof(ICommand), typeof(ComboBoxWithCommand), new PropertyMetadata((ICommand)null, new PropertyChangedCallback(CommandChanged))); public ICommand Command { get { return (ICommand)GetValue(CommandProperty); } set { SetValue(CommandProperty, value); } } public static readonly DependencyProperty CommandTargetProperty = DependencyProperty.Register("CommandTarget", typeof(IInputElement), typeof(ComboBoxWithCommand), new PropertyMetadata((IInputElement)null)); public IInputElement CommandTarget { get { return (IInputElement)GetValue(CommandTargetProperty); } set { SetValue(CommandTargetProperty, value); } } public static readonly DependencyProperty CommandParameterProperty = DependencyProperty.Register("CommandParameter", typeof(object), typeof(ComboBoxWithCommand), new PropertyMetadata((object)null)); public object CommandParameter { get { return (object)GetValue(CommandParameterProperty); } set { SetValue(CommandParameterProperty, value); } } public ComboBoxWithCommand() : base() { } private static void CommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { ComboBoxWithCommand cb = (ComboBoxWithCommand)d; cb.HookUpCommand((ICommand)e.OldValue, (ICommand)e.NewValue); } private void HookUpCommand(ICommand oldCommand, ICommand newCommand) { if (oldCommand != null) { RemoveCommand(oldCommand, newCommand); } AddCommand(oldCommand, newCommand); } private void RemoveCommand(ICommand oldCommand, ICommand newCommand) { EventHandler handler = CanExecuteChanged; oldCommand.CanExecuteChanged -= handler; } private void AddCommand(ICommand oldCommand, ICommand newCommand) { EventHandler handler = new EventHandler(CanExecuteChanged); canExecuteChangedHandler = handler; if (newCommand != null) { newCommand.CanExecuteChanged= canExecuteChangedHandler; } } private void CanExecuteChanged(object sender, EventArgs e) { if (this.Command != null) { RoutedCommand command = this.Command as RoutedCommand; // If a RoutedCommand. if (command != null) { if (command.CanExecute(this.CommandParameter, this.CommandTarget)) { this.IsEnabled = true; } else { this.IsEnabled = false; } } // If a not RoutedCommand. else { if (Command.CanExecute(CommandParameter)) { this.IsEnabled = true; } else { this.IsEnabled = false; } } } } protected override void OnSelectionChanged(SelectionChangedEventArgs e) { base.OnSelectionChanged(e); if (this.Command != null) { RoutedCommand command = this.Command as RoutedCommand; if (command != null) { command.Execute(this.CommandParameter, this.CommandTarget); } else { ((ICommand)Command).Execute(CommandParameter); } } }}
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