私が昨日Prism フォーラムCommandParameterBehaviorに投稿したものを使用できるかもしれません。原因の変更が再クエリされるという欠落している動作を追加します。CommandParameterCommand
PropertyDescriptor.AddValueChanged後でPropertyDescriptor.RemoveValueChanged. _ ekement がアンロードされたときにハンドラーを登録解除することで、これを修正しようとしています。
IDelegateCommandPrism を使用していない限り (そして、Prism ライブラリに私と同じ変更を加えたい場合は) 、おそらくそれらを削除する必要があります。また、ここでは一般的に s を使用しないことに注意してくださいRoutedCommand(ほとんどすべての場合に Prism を使用します) ため、既知の宇宙などを破壊するある種の量子波動関数の崩壊カスケードがDelegateCommand<T>への呼び出しによって引き起こされたとしても、私に責任を負わせないでください。CommandManager.InvalidateRequerySuggested
using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Input;
namespace Microsoft.Practices.Composite.Wpf.Commands
{
/// <summary>
/// This class provides an attached property that, when set to true, will cause changes to the element's CommandParameter to
/// trigger the CanExecute handler to be called on the Command.
/// </summary>
public static class CommandParameterBehavior
{
/// <summary>
/// Identifies the IsCommandRequeriedOnChange attached property
/// </summary>
/// <remarks>
/// When a control has the <see cref="IsCommandRequeriedOnChangeProperty" />
/// attached property set to true, then any change to it's
/// <see cref="System.Windows.Controls.Primitives.ButtonBase.CommandParameter" /> property will cause the state of
/// the command attached to it's <see cref="System.Windows.Controls.Primitives.ButtonBase.Command" /> property to
/// be reevaluated.
/// </remarks>
public static readonly DependencyProperty IsCommandRequeriedOnChangeProperty =
DependencyProperty.RegisterAttached("IsCommandRequeriedOnChange",
typeof(bool),
typeof(CommandParameterBehavior),
new UIPropertyMetadata(false, new PropertyChangedCallback(OnIsCommandRequeriedOnChangeChanged)));
/// <summary>
/// Gets the value for the <see cref="IsCommandRequeriedOnChangeProperty"/> attached property.
/// </summary>
/// <param name="target">The object to adapt.</param>
/// <returns>Whether the update on change behavior is enabled.</returns>
public static bool GetIsCommandRequeriedOnChange(DependencyObject target)
{
return (bool)target.GetValue(IsCommandRequeriedOnChangeProperty);
}
/// <summary>
/// Sets the <see cref="IsCommandRequeriedOnChangeProperty"/> attached property.
/// </summary>
/// <param name="target">The object to adapt. This is typically a <see cref="System.Windows.Controls.Primitives.ButtonBase" />,
/// <see cref="System.Windows.Controls.MenuItem" /> or <see cref="System.Windows.Documents.Hyperlink" /></param>
/// <param name="value">Whether the update behaviour should be enabled.</param>
public static void SetIsCommandRequeriedOnChange(DependencyObject target, bool value)
{
target.SetValue(IsCommandRequeriedOnChangeProperty, value);
}
private static void OnIsCommandRequeriedOnChangeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (!(d is ICommandSource))
return;
if (!(d is FrameworkElement || d is FrameworkContentElement))
return;
if ((bool)e.NewValue)
{
HookCommandParameterChanged(d);
}
else
{
UnhookCommandParameterChanged(d);
}
UpdateCommandState(d);
}
private static PropertyDescriptor GetCommandParameterPropertyDescriptor(object source)
{
return TypeDescriptor.GetProperties(source.GetType())["CommandParameter"];
}
private static void HookCommandParameterChanged(object source)
{
var propertyDescriptor = GetCommandParameterPropertyDescriptor(source);
propertyDescriptor.AddValueChanged(source, OnCommandParameterChanged);
// N.B. Using PropertyDescriptor.AddValueChanged will cause "source" to never be garbage collected,
// so we need to hook the Unloaded event and call RemoveValueChanged there.
HookUnloaded(source);
}
private static void UnhookCommandParameterChanged(object source)
{
var propertyDescriptor = GetCommandParameterPropertyDescriptor(source);
propertyDescriptor.RemoveValueChanged(source, OnCommandParameterChanged);
UnhookUnloaded(source);
}
private static void HookUnloaded(object source)
{
var fe = source as FrameworkElement;
if (fe != null)
{
fe.Unloaded += OnUnloaded;
}
var fce = source as FrameworkContentElement;
if (fce != null)
{
fce.Unloaded += OnUnloaded;
}
}
private static void UnhookUnloaded(object source)
{
var fe = source as FrameworkElement;
if (fe != null)
{
fe.Unloaded -= OnUnloaded;
}
var fce = source as FrameworkContentElement;
if (fce != null)
{
fce.Unloaded -= OnUnloaded;
}
}
static void OnUnloaded(object sender, RoutedEventArgs e)
{
UnhookCommandParameterChanged(sender);
}
static void OnCommandParameterChanged(object sender, EventArgs ea)
{
UpdateCommandState(sender);
}
private static void UpdateCommandState(object target)
{
var commandSource = target as ICommandSource;
if (commandSource == null)
return;
var rc = commandSource.Command as RoutedCommand;
if (rc != null)
{
CommandManager.InvalidateRequerySuggested();
}
var dc = commandSource.Command as IDelegateCommand;
if (dc != null)
{
dc.RaiseCanExecuteChanged();
}
}
}
}