扩展器IsExpanded绑定

Question

在以下代码中:

http://msdn.microsoft.com/en-us/library/ms754027.aspx

如何将IsExpanded绑定到MyData对象列表,其中每个对象都具有IsExpanded属性？

<Expander IsExpanded={Binding Path=IsExpanded, Mode=TwoWay} />

这不起作用!

MyData is List<GroupNode>;

GroupNode是一个包含通知属性已更改属性IsExpanded的类.

因此,如果我手动打开其中一个扩展器,它应该将IsExpanded属性设置为该MyData的GroupNode的true.

Answer 1

这不是很容易做到,因为DataContext的GroupItem是一个实例CollectionViewGroup,这个类不具有IsExpanded财产.但是,您可以在其中指定转换器GroupDescription,允许您返回组的"名称"(CollectionViewGroup.Name属性)的自定义值.这个"名字"可以是任何东西; 在您的情况下,您需要它是一个包装组名称的类(例如分组键)并具有IsExpanded属性:

这是一个例子:

public class ExpandableGroupName : INotifyPropertyChanged
{
    private object _name;
    public object Name
    {
        get { return _name; }
        set
        {
            if (_name != value)
            {
                _name = value;
                OnPropertyChanged("Name");
            }
        }
    }

    private bool? _isExpanded = false;
    public bool? IsExpanded
    {
        get { return _isExpanded; }
        set
        {
            if (_isExpanded != value)
            {
                _isExpanded = value;
                OnPropertyChanged("IsExpanded");
            }
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

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

    #endregion

    public override bool Equals(object obj)
    {
        return object.Equals(obj, _name);
    }

    public override int GetHashCode()
    {
        return _name != null ? _name.GetHashCode() : 0;
    }

    public override string ToString()
    {
        return _name != null ? _name.ToString() : string.Empty;
    }
}

这是转换器:

public class ExpandableGroupNameConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return new ExpandableGroupName { Name = value };
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var groupName = value as ExpandableGroupName;
        if (groupName != null)
            return groupName.Name;
        return Binding.DoNothing;
    }

    #endregion
}

在XAML中,只需声明分组如下:

<my:ExpandableGroupNameConverter x:Key="groupConverter" />
<CollectionViewSource x:Key='src' 
                      Source="{Binding Source={StaticResource MyData}, 
                               XPath=Item}">
  <CollectionViewSource.GroupDescriptions>
    <PropertyGroupDescription PropertyName="@Catalog" Converter="{StaticResource groupConverter}" />
  </CollectionViewSource.GroupDescriptions>
</CollectionViewSource>

然后绑定IsExpanded属性:

<Expander IsExpanded={Binding Path=Name.IsExpanded} />