从UserControl外部绑定到命令

Question

我有一个简单的UserControl包含Label,ComboBox和Button.简而言之,它几乎可以在我的几乎所有视图中使用,每次使用不同的ItemsSource和CreateItemCommand使用Bindings到我的ViewModel属性.

Label和ComboBox是另一个UserControl(LabeledComboBox)的一部分,它工作正常.

问题是,当我尝试在包含我的UserControl的窗口中绑定命令时,我得到以下异常:

无法在'MutableComboBox'类型的'CreateItemCommand'属性上设置'绑定'.'绑定'只能在DependencyObject的DependencyProperty上设置.

这是MutableComboBox的XAML:

<UserControl x:Class="Albo.Presentation.Templates.MutableComboBox"
x:Name="MCB"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:uc="clr-namespace:Albo.Presentation.Templates" >
<StackPanel Height="25" Orientation="Horizontal">
    <uc:LabeledComboBox x:Name="ComboBoxControl"
        Label = "{Binding ElementName=MCB, Path=Label}"
        ItemsSource="{Binding ElementName=MCB, Path=ItemsSource}"
        SelectedItem="{Binding ElementName=MCB, Path=SelectedItem}" />
    <Button x:Name="CreateItemButton"
        Grid.Column="1" Width="25" Margin="2,0,0,0"
        Content="+" FontFamily="Courier" FontSize="18" 
        VerticalContentAlignment="Center"
        Command="{Binding ElementName=MCB, Path=CreateItemCommand}"/>
</StackPanel>
</UserControl>

这是它的代码隐藏:

public partial class MutableComboBox : UserControl
{
    public MutableComboBox()
    {
        InitializeComponent();
    }

    public string Label
    {
        get { return this.ComboBoxControl.Label; }
        set { this.ComboBoxControl.Label = value; }
    }

    #region ItemsSource dependency property
    public static readonly DependencyProperty ItemsSourceProperty =
        ItemsControl.ItemsSourceProperty.AddOwner(
            typeof(MutableComboBox),
            new PropertyMetadata(MutableComboBox.ItemsSourcePropertyChangedCallback)
        );

    public IEnumerable ItemsSource
    {
        get { return (IEnumerable)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    public static void ItemsSourcePropertyChangedCallback(
        DependencyObject controlInstance,
        DependencyPropertyChangedEventArgs e)
    {
        MutableComboBox myInstance = (MutableComboBox)controlInstance;

        myInstance.ComboBoxControl.ItemsSource = (IEnumerable)e.NewValue;
    } 
    #endregion // ItemsSource dependency property

    #region SelectedItem dependency property
    // It has just the same logic as ItemsSource DP.
    #endregion SelectedItem dependency property

    #region CreateItemCommand dependency property

    public static readonly DependencyProperty CreateItemCommandProperty =
        DependencyProperty.Register(
            "MutableComboBoxCreateItemCommandProperty",
            typeof(ICommand),
            typeof(MutableComboBox)
        );

    public ICommand CreateItemCommand
    {
        get { return (ICommand)GetValue(CreateItemCommandProperty); }
        set { SetValue(CreateItemCommandProperty,value); }
    }

    #endregion // CreateItem dependency property
}

如您所见,我使用两种不同的方法来注册我的DP:ItemsSource来自ItemsControl DP,CreateItemCommand是由DependencyProperty.Register(...)创建的.我尝试使用Button.CommandProperty.AddOwner(...)但有相同的异常.

这是我尝试绑定的方式:

<Window ...
    xmlns:uc="clr-namespace:Albo.Presentation.Templates">
    <uc:MutableComboBox Label="Combo" 
        ItemsSource="{Binding Path=Recipients}"
        CreateItemCommand="{Binding Path=CreateNewRecipient}"/>
</Window>

窗口的DataContext设置为适当的ViewModel,它提供了一个ObservableCollection的Recipients和一个ICommand CreateNewRecipient作为简单属性.

我究竟做错了什么？在这种特殊情况下,我唯一想要的是公开一个Button.Command属性,以便在我的UserControl之外使用,就像ItemsSource一样.我试图以错误的方式使用命令吗？如何从其他控件或窗口绑定到UserControls的命令？

考虑一下这个Command和DependencyProperty的新东西.任何帮助,将不胜感激.用了一整天的Google搜索,在我的案例中找不到任何可用的东西.原谅我的英语.

Answer 1

您已为依赖项属性注册了错误的名称.它应该是:

public static readonly DependencyProperty CreateItemCommandProperty =
        DependencyProperty.Register(
            "CreateItemCommand",
            typeof(ICommand),
            typeof(MutableComboBox)
        );

请注意该字符串是"CreateItemCommand".您应该阅读此MSDN文档,以获取有关依赖项属性约定的详细信息.