WPF 将过滤后的 ObservableCollection ICollectionView 绑定到 Combobox

Question

我想根据类型（类型 AddPoint）将 ObservableCollection 过滤为子集，并希望它按升序排列，没有重复。我的基类是 ModelBase，带有子类 AddPoint、Time、Repeat 等... ObservableCollection MotionSequenceCollection 将以任何顺序填充这些类型，并且有些将是重复的。

我已经尝试了几次不同的时间，并在下面我“拉”出的 ICollectionView 属性中显示了它们：Bind subset of collection。

可观察的集合

private ObservableCollection<ModelBase> _motionSequenceCollection = 
        new ObservableCollection<ModelBase>();

    public ObservableCollection<ModelBase> MotionSequenceCollection
    {
        get
        {
            return _motionSequenceCollection;
        }

        set
        {
            if (_motionSequenceCollection == value)
            {
                return;
            }

            var oldValue = _motionSequenceCollection;
            _motionSequenceCollection = value;

            // Update bindings, no broadcast
            RaisePropertyChanged();
        }
    }

    public ICollectionView Location
    {
        get
        {
             var location = CollectionViewSource.GetDefaultView(_motionSequenceCollection);

            //DOES NOT WORK.  PROBLEM: GetType() creates type of system.type() and AddPoint, which don't work.  Need a cast, or something??  
            // found at https://stackoverflow.com/questions/9621393/bind-subset-of-collection  The problem is that there is an error:
            //    Cannot apply operator '==' to operands of type 'System.Type' and 'MotionSeq.Model.AddPoint',
            //    candidates are:
            //          bool ==(System.Reflection.MemberInfo, System.Reflection.memberInfo) (in class MemberInfo)
            //          bool ==(System.type, System.Type) (in class Type)
            //location.Filter = p => (p as ModelBase).GetType() == AddPoint;

            //DOES NOT WORK.  PROBLEM: Affects the main collection and won't let TIME type added.
            //location.Filter = o1 => (o1 is AddPoint);

            //DOES NOT WORK.  PROBLEM: Sorts fine, but also sorts MotionSequenceCollection!!  What up w/ that!?  
            //location.SortDescriptions.Add(new SortDescription("AddPointClassName", ListSortDirection.Ascending));

            //DOES NOT WORK.  PROBLEM: MotionSequenceCollection does not update.
            //location.Filter = p => (p as ModelBase) == AddPoint;

            //DOES NOT WORK.  PROBLEM: Source is not instantiated(?) and exmaple from stackoverflow and not sure how that got there in the first place.
            //source.Filter = p => (p as ModelBase).GetType() == "AddPoint";
            //return source;

            return location;
        }
    }

Answer 1

所有集合都有一个默认的 CollectionView。 WPF 始终绑定到视图而不是集合。如果直接绑定到集合，WPF 实际上会绑定到该集合的默认视图。此默认视图由​​集合的所有绑定共享，这会导致集合的所有直接绑定共享一个默认视图的排序、过滤器、组和当前项特性。

尝试创建CollectionViewSource 并将其过滤逻辑设置如下：

//create it as static resource and bind your ItemsControl to it
<CollectionViewSource x:Key="csv" Source="{StaticResource MotionSequenceCollection}" 
                  Filter="CollectionViewSource_Filter">
    <CollectionViewSource.GroupDescriptions>
       <PropertyGroupDescription PropertyName="YYY"/>
    </CollectionViewSource.GroupDescriptions>
    <CollectionViewSource.SortDescriptions>
         <scm:SortDescription PropertyName="YYY" Direction="Ascending"/>
    </CollectionViewSource.SortDescriptions>
</CollectionViewSource> 

private void CollectionViewSource_Filter(object sender, FilterEventArgs e)
{
    var t = e.Item as ModelBase;
    if (t != null)

    {
        //use your filtering logic here

    }
}

Answer 2

按类型过滤很容易。这应该有效：

location.Filter = p => p.GetType() == typeof(AddPoint);

排序也很容易。您需要做的就是实现IComparer 并将其分配给集合视图的CustomSort 属性。

没有简单的方法可以删除重复项（我不知道）。我建议你在其他地方做。例如，您可以区分您的基础集合。