根據組別ItemCount排序羣組

Question

在ListCollectionView上，我只是添加新的GroupDescriptions。 但我正在尋找一種方法來根據組的ItemCount對它們進行排序。

所以在第一個位置，我會得到最多的項目組。

Answer 1

你可以將這些組包裝在另一個視圖中並對其進行排序。

XAML例如：

<CollectionViewSource x:Key="Items2" Source="{Binding Groups, 
                 Source={StaticResource Items}}"> 
    <CollectionViewSource.SortDescriptions> 
     <cm:SortDescription PropertyName="ItemCount" Direction="Descending"/> 
    </CollectionViewSource.SortDescriptions> 
</CollectionViewSource> 

Answer 2

我創建了一個自定義的ListCollectionView使頂級組排序可以使用一個偉大的圖書館System.Linq.Dynamic：

Public Class ListCollectionViewEx 
    Inherits ListCollectionView 
    Private _groupSortDescriptions As SortDescriptionCollection 
    Private _groups As ReadOnlyObservableCollection(Of Object) 

    Public Overridable ReadOnly Property GroupSortDescriptions As SortDescriptionCollection 
     Get 
      Return Me._groupSortDescriptions 
     End Get 
    End Property 

    Public Overrides ReadOnly Property Groups As System.Collections.ObjectModel.ReadOnlyObservableCollection(Of Object) 
     Get 
      If Me._groupSortDescriptions.Count > 0 Then 
       If Me._groups Is Nothing AndAlso 
        MyBase.Groups IsNot Nothing Then 
        Dim qs As String = String.Join(
         ",", 
         Me._groupSortDescriptions. 
         Select(Function(gsd) String.Format("{0} {1}", gsd.PropertyName, If(gsd.Direction = ListSortDirection.Ascending, "ASC", "DESC"))). 
         ToArray) 

        Dim sortedGroups = MyBase.Groups. 
         Select(Function(g) DirectCast(g, CollectionViewGroup)). 
         AsQueryable.OrderBy(qs). 
         AsEnumerable 

        If sortedGroups IsNot Nothing AndAlso 
         sortedGroups.Count > 0 Then 
         Me._groups = New ReadOnlyObservableCollection(Of Object)(New ObservableCollection(Of Object)(sortedGroups)) 
        End If 
       End If 

       Return Me._groups 
      End If 

      Return MyBase.Groups 
     End Get 
    End Property 

    Public Sub New(collection As IEnumerable) 
     MyBase.New(collection) 
     Me._groupSortDescriptions = New SortDescriptionCollection() 
    End Sub 
End Class 

用法：

View.GroupSortDescriptions.Add(New SortDescription("ItemCount", ListSortDirection.Descending))