WPF UserControls：有一个仅在 UserControl 内部可用的命令

Question

我正在做一个 WPF UserControl。

在这个 UserControl 内部，我有几个 Button 可以在特定条件下使用，因此将它们绑定到命令是完美的。

这些按钮调用的命令不应该在用户控件之外可用。

如果我将我的命令设为私有，UserControl 的 XAML 表示他想要公共成员。

那么，怎样才能让一个 UserControl 内部有多个命令，但在 UserControl 之外不可用？

例子：

<Wizard CanGoPrevious="{Binding SomeViewModelProperty}">
    <WizardPage>
        <TextBlock>Page one</TextBlock>
    </WizardPage>
</Wizard>

向导的 XAML：

<DockPanel DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type wizard:Wizard}}}" LastChildFill="True">
    <StackPanel Orientation="Horizontal" DockPanel.Dock="Bottom" HorizontalAlignment="Right"> 
        <Button Content="{Binding PreviousButtonText}" Command="{Binding GoToPreviousPageCommand}"/>
    </StackPanel>
    <ContentControl ></ContentControl>
</DockPanel>

背后的向导代码：

//Protected doesn't work. Also, this command should not be available outside of the Wizard `UserControl`
protected DelegateCommand GoToPreviousPageCommand { get; set; } 

在构造函数中是这样赋值的

GoToPreviousPageCommand = new DelegateCommand(GoToPreviousPage, CanGoToPreviousPage);


    private void GoToPreviousPage()
    {
        //[...]
    }

    private bool CanGoToNextPage()
    {
        //Some usage of the Wizard's DP:
        return CanGoPrevious //&& some other stuff
    }

Answer 1

编辑：添加示例代码（应该能够复制/过去/运行）： 将命令保留为公开，但将您的 ViewModel 设为内部将使命令对外部代码不可见！

<Window x:Class="InternalCommandUsageSample.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:InternalCommandUsageSample"
    Title="MainWindow" Height="350" Width="525">
<local:MyUserControl/>

测试用户控件的窗口后面的代码：

using System.Windows;

namespace InternalCommandUsageSample
{
public partial class MainWindow : Window
{
    public MainWindow()
    {
        var vm = new MyViewModel();
        DataContext = vm;

        InitializeComponent();
    }
}

}

用户控制：

<UserControl x:Class="InternalCommandUsageSample.MyUserControl"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<StackPanel>
    <TextBlock Text="{Binding Message, Mode=OneWay}"/>
    <Button Content="Test Me" Command="{Binding TestMeCommand}"/>
</StackPanel>

以及在您的程序集之外不可见的内部视图模型：

internal class MyViewModel : INotifyPropertyChanged
{
    private string _message = "click the button";
    private DelegateCommand _cmd;

    public DelegateCommand TestMeCommand
    {
        get
        {
            return _cmd ?? (_cmd = new DelegateCommand(cmd => { Message = "Your button click envoked an internal command"; }));
        }
    }

    public string Message
    {
        get { return _message; }
        set
        {
            if (_message != value)
            {
                _message = value;
                OnPropertyChanged("Message");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

编辑：在 cmets 中询问了关于如何使用 suer 控件和视图模型的依赖属性的附加问题。方法有很多，这是其中之一：

        public string MySampleDependencyProperty
    {
        get { return (string)GetValue(MySampleDependencyPropertyProperty); }
        set { SetValue(MySampleDependencyPropertyProperty, value); }
    }

    public static readonly DependencyProperty MySampleDependencyPropertyProperty = 
        DependencyProperty.Register("MySampleDependencyProperty", typeof(string), 
        typeof(MyUserControl),
        new FrameworkPropertyMetadata("", 
            FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, (o, e) => ((MyUserControl)o).OnMySampleDependencyPropertyChanged()));

    private void OnMySampleDependencyPropertyChanged()
    {
        viewMdoel.WhateverProperty = MySampleDependencyProperty;
    }