尽管 ICommand.CanExecute 的计算结果为真，但按钮已禁用

Question

我有两个 WPF 项目，一个是 .Net 4.7 dll，另一个是桌面应用程序。

在我的 dll 中我有 classes Viewport2D 和 ViewportCommands

public static class ViewportCommands
{
    public static RoutedCommand ResetView { get; } = new RoutedCommand(nameof(ResetView), typeof(ViewportCommands));
    public static RoutedCommand ZoomFit { get; } = new RoutedCommand(nameof(ZoomFit), typeof(ViewportCommands));
}

我的 Viewport2D 在 ctor 中绑定了那些命令：

    public Viewport2D()
    {
        ...

        CommandBindings.Add(new CommandBinding(NavigationCommands.IncreaseZoom, ExecuteZoomIn, CanZoom));
        CommandBindings.Add(new CommandBinding(NavigationCommands.DecreaseZoom, ExecuteZoomOut, CanZoom));
        CommandBindings.Add(new CommandBinding(ViewportCommands.ZoomFit, (o, e) => ZoomFit(), CanZoom));
        CommandBindings.Add(new CommandBinding(ViewportCommands.ResetView, (o, e) => Reset(), (o, e) => e.CanExecute = true));

        ...
    }

如您所见，ResetView 命令的计算结果始终为真。在大多数情况下，ZoomFit 命令的计算结果也为真（并且两个函数都被调用，我已经检查过了）。

在我的 WPF 应用程序中，我使用了这个控件：

  <controls1:Viewport2D x:Name="Zoombox" ...>
    <controls1:Viewport2D.InputBindings>
      <MouseBinding Gesture="{wpfUtils:MouseWheel Direction=Down}" Command="DecreaseZoom" CommandTarget="{Binding ElementName=Zoombox}" />
      <MouseBinding Gesture="{wpfUtils:MouseWheel Direction=Up}" Command="IncreaseZoom" CommandTarget="{Binding ElementName=Zoombox}" />
    </controls1:Viewport2D.InputBindings>
    ...
  </controls1:Viewport2D>

  ...

  <Button Content="100%" Width="70" Command="controls1:ViewportCommands.ResetView" />
  <Button Content="Zoom Fit" Width="70" Command="controls1:ViewportCommands.ZoomFit" />

IncreaseZoom 和 DecreaseZoom 来自 NavigationCommands class（.Net 的一部分）。

上面代码片段中的两个按钮始终处于禁用状态，尽管它们应该处于启用状态。但是，使用两个缩放命令进行缩放都可以正常工作。

我做错了什么？

Answer 1

我做个测试如果绑定在用户控件中，则它不起作用；如果我更改为 MainWindow，它会起作用...两者都相同 xaml ----好----

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        CommandBindings.Add(new CommandBinding(ViewportCommands.ZoomFit, (o, e) => ZoomFit(), (o, e) => e.CanExecute = true));
        CommandBindings.Add(new CommandBinding(ViewportCommands.ResetView, (o, e) => Reset(), (o, e) => e.CanExecute = true));
    }


    public void ZoomFit()
    {

    }
    public void Reset()
    {

    }

}
 public static class ViewportCommands
    {
        public static RoutedCommand ResetView { get; } = new RoutedCommand(nameof(ResetView), typeof(ViewportCommands));
        public static RoutedCommand ZoomFit { get; } = new RoutedCommand(nameof(ZoomFit), typeof(ViewportCommands));
    }

----不好----

    <Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <local:UserControl1></local:UserControl1>
        <Button Content="100%" Width="70" Command="local:ViewportCommands.ResetView" />
        <Button Content="Zoom Fit" Width="70" Command="local:ViewportCommands.ZoomFit" />
    </StackPanel>
</Window>


public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();

            CommandBindings.Add(new CommandBinding(ViewportCommands.ZoomFit, (o, e) => ZoomFit(), (o, e) => e.CanExecute = true));
            CommandBindings.Add(new CommandBinding(ViewportCommands.ResetView, (o, e) => Reset(), (o, e) => e.CanExecute = true));
        }


        public void ZoomFit()
        {

        }
        public void Reset()
        {

        }
    }

尽管 ICommand.CanExecute 的计算结果为真，但按钮已禁用

Button disabled although ICommand.CanExecute evaluates to true

.net

c#

wpf

commandbinding