Question

在以下代码中：绑定到UIElement的{{1}}在从集合中添加或删除项目时不会更新。

具体做法是：

Person对象包含ObservableCollection属性Links，它可以包含任意数量的可以引用其他Person对象的Link对象。 Person和Link类都实现了ObservableCollection接口。

INotifyPropertyChanged

Links和Crowd类都是ObservableCollections的子类。 Crowd对象是Person对象的ObservableCollection。 Links对象是Link对象的ObservableCollection：

public class Person: INotifyPropertyChanged
{
    // INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    // fields
    private string id = "";
    private string firstName = "";
    private string lastName = "";
    private Links links = new Links();

    // properties firing PropertyChanged events 
    public string ID
    {
        get { return id; }
        set
        {
            if (value != this.id)
            {
                this.id = value;
                NotifyPropertyChanged("ID");
            }
        }
    }
    public string FirstName
    {
        get { return firstName; }
        set
        {
            if (value != this.firstName)
            {
                this.firstName = value;
                NotifyPropertyChanged("FirstName");
            }
        }
    }
    public string LastName
    {
        get { return lastName; }
        set
        {
            if (value != this.lastName)
            {
                this.lastName = value;
                NotifyPropertyChanged("LastName");
            }
        }
    }
    public Links Links
    {
        get { return links; }
        set
        {
            if (value != this.links)
            {
                this.links = value;
                NotifyPropertyChanged("Links");
            }
        }
    }

    // constructors
    public Person()
    {
        new Person("", "", "");
    }
    public Person(string id, string firstName, string lastName)
    {
        this.ID = id;
        this.FirstName = firstName;
        this.LastName = lastName;
    }

}



public enum LinkState { none, oneway, twoway }

public class Link: INotifyPropertyChanged
{

    // INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    // fields
    private Person fromWhom;
    private Person toWhom;

    // properties firing PropertyChanged events 
    public Person FromWhom
    {
        get { return fromWhom; }
        set
        {
            if (value != this.fromWhom)
            {
                this.fromWhom = value;
                NotifyPropertyChanged("FromWhom");
            }
        }
    }
    public Person ToWhom
    {
        get { return toWhom; }
        set
        {
            if (value != this.toWhom)
            {
                this.toWhom = value;
                NotifyPropertyChanged("ToWhom");
            }
        }
    }

    // constructors
    public Link()
    {
        new Link(null, null);
    }
    public Link(Person fromWhom, Person toWhom)
    {
        this.FromWhom = fromWhom;
        this.ToWhom = toWhom;
    }

}

WP7应用程序的MainPage类是PhoneApplicationPage类的子类。它包含两个属性：人群，群众对象和我，一个Person对象。

以下XAML应显示： a）从Me对象到Crowd中的Person对象的链接数，以及 b）人群中Person对象的列表。

 public class Links: ObservableCollection<Link>
    {

    }


    public class Crowd : ObservableCollection<Person>
    {

    }

但是，当从Me.Links（ObserverableCollection）添加或删除Link对象时，名为“LinkCounter”的Textblock不会更新，即使它绑定到ObservableCollection。

由于Me.Links ObservableCollection在添加新链接时被更改，或者现有链接被删除，我认为绑定到它的任何内容都应该更新。

对此问题的任何帮助将不胜感激。感谢。

Answer 1

此处不会触发数据绑定，因为您没有更改对Links集合的引用。而不是绑定到引用并使用转换器尝试使用

<TextBlock x:Name=LinkCounter  Text="{Binding ElementName=ThePage, Path=Me.Links.Count" />

从ObservableCollection添加或删除项时，不会更新绑定到ObservableCollection的WP7 UIElement属性

1 个答案: