UserControl中的wpf绑定集合属性

Question

我有一个自定义UserControl,其中包含自定义对象的集合.

public class Question : FrameworkElement
{
    public readonly static DependencyProperty FullNameProperty =
        DependencyProperty.Register("FullName", typeof(string), typeof(Question));

    public readonly static DependencyProperty ShortNameProperty =
        DependencyProperty.Register("ShortName", typeof(string), typeof(Question));

    public readonly static DependencyProperty RecOrderProperty =
        DependencyProperty.Register("RecOrder", typeof(int), typeof(Question));

    public readonly static DependencyProperty AnswerProperty =
        DependencyProperty.Register("Answer", typeof(string), typeof(Question));

    public string FullName
    {
        get { return (string)GetValue(FullNameProperty); }
        set { SetValue(NameProperty, value); }
    }

    public string ShortName
    {
        get { return (string)GetValue(ShortNameProperty); }
        set { SetValue(ShortNameProperty, value); }
    }

    public string Answer
    {
        get { return (string)GetValue(AnswerProperty); }
        set { SetValue(AnswerProperty, value); }
    }

    public int RecOrder
    {
        get { return (int)GetValue(RecOrderProperty); }
        set { SetValue(RecOrderProperty, value); }
    }
}

在我的控制代码后面,我有

public readonly static DependencyProperty QuestionsProperty =
        DependencyProperty.Register("Questions", typeof(ObservableCollection<Question>), typeof(FormQuestionReportViewer), 
        new PropertyMetadata(new ObservableCollection<Question>()));


     public ObservableCollection<Question> Questions
     {
        get { return GetValue(QuestionsProperty) as ObservableCollection<Question>; }
        set { SetValue(QuestionsProperty, value); }
     }

在xaml标记中,我可以像这样定义我的控件

    <custom:CustomControl>
        <custom:CustomControl.Questions>
            <custom:Question FullName="smth text" ShortName="smth text" RecOrder="1" Answer="Yes" />
            <custom:Question FullName="smth text" ShortName="smth text" RecOrder="2" Answer="Yes" />
        </custom:CustomControl.Questions>          
    </custom:CustomControl>

它运行良好,但我想在xaml中绑定我的集合属性,就像这样

    <custom:CustomControl>
        <custom:CustomControl.Questions Items="{binding Path=Questions}">
            <custom:Question FullName="{binding Name}" ShortName="{binding ShortName}" RecOrder="{binding RecOrder}" Answer={binding Answer}" /> 
        </custom:CustomControl.Questions>          
    </custom:CustomControl>

我怎么能做这个约束？

Answer 1

您必须公开两个单独的属性,就像ItemsControl具有Items和ItemsSource属性的属性一样.看起来您希望能够使用绑定添加项目,并通过添加到您的集合中进行显式添加.此行为与ItemsControl不同,后者仅允许您使用Items或ItemsSource属性,但不能同时使用两者.

没有什么可以阻止您添加对指定项目的两种方式的支持,但是对您来说这将是更多的工作.

首先,您需要一个DependencyProperty,例如IEnumerable QuestionsSource,您可以绑定到:

public readonly static DependencyProperty QuestionsSourceProperty =
    DependencyProperty.Register("QuestionsSource",
        typeof(IEnumerable),
        typeof(FormQuestionReportViewer), 
        new PropertyMetadata(null));

 public IEnumerable QuestionsSource
 {
    get { return GetValue(QuestionsSourceProperty) as IEnumerable; }
    set { SetValue(QuestionsSourceProperty, value); }
 }

第二,您需要一个常规的CLR属性,例如ObservableCollection<Question> Questions,您可以显式添加项目:

private ObservableCollection<Question> questions = new ObservableCollection<Question>();
public ObservableCollection<Question> Questions
 {
    get { return questions; }
 }

然后你可以像这样使用这些属性:

<custom:CustomControl QuestionsSource="{Binding Path=Questions}">
    <custom:CustomControl.Questions>
        <custom:Question FullName="{binding Name}" ShortName="{binding ShortName}" RecOrder="{binding RecOrder}" Answer={binding Answer}" /> 
    </custom:CustomControl.Questions>          
</custom:CustomControl>

当您想要获得完整的项目列表时,需要额外的工作.您需要将两个集合合并为一个集合.此统一集合将作为第三个属性公开,它返回只读集合.