NotifyCollectionChangedAction.Reset清空组合框文本

我有一个 ComboBox ,这是 ItemsSource 设置为继承的对象 ObservableCollection

因为有时会有大量的新数据,所以我不使用 Add 可观测集合 ,但我使用以下代码:

For Each itm In MyNewItems 
   Items.Add(itm)
Next
MyBase.OnPropertyChanged(New PropertyChangedEventArgs("Count"))
OnPropertyChanged(New PropertyChangedEventArgs("Items[]"))

'下一行导致问题'

OnCollectionChanged(New NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset))

Text 的 组合框

如果我删除了那一行,那么问题就解决了,但是这些项显示了旧数据,因为 组合框 不知道有新的数据

赞赏地

嗨,根据要求,我把相关代码贴在这里

1:Xaml,非常简单:

<Window x:Class="dlgTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mch="clr-namespace:Machshevet.Windows;assembly=Machshevet"  >
<StackPanel>
    <TextBlock Text="{Binding CaseID}"/>
    <mch:TestPick Name="cmbTest"   SelectedValuePath="ID"  DisplayMemberPath="Name" SelectedValue="{Binding CaseID}"  IsEditable="True"  IsTextSearchEnabled="False"   />
</StackPanel>    
</Window>

Public Class TestPick
    Inherits ComboBox
    Dim usertyped As Boolean

    Function Query() As IQueryable
        Dim txt = ""
        Dispatcher.Invoke(Sub() txt = Text)
        Dim ret = GetSlimContext.Query("viwCase").Select("new (ID,Name,ClientName,SubjectName)")
        If txt <> "" AndAlso usertyped Then ret = ret.TextFiltered(txt)
        Return ret
    End Function

    Private Sub EntityPick_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
        Dim qs = New QuerySource(Function() Query())
        Me.ItemsSource = qs
        qs.Control = Me
        qs.ShouldRefresh = Function() True
    End Sub

    Private Sub EntityPick_PreviewTextInput(sender As Object, e As TextCompositionEventArgs) Handles Me.PreviewTextInput
        usertyped = True
    End Sub

    Private Sub TestPick_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles Me.SelectionChanged
        If e.AddedItems.None Then
            Dim a = 1
        End If
    End Sub
End Class

3:执行所有繁重工作的QuerySource类

   Public Class QuerySource
    Inherits ObjectModel.ObservableCollection(Of Object)
    Event Refreshed(sender As QuerySource, e As EventArgs)
    Property RefreshSpan As TimeSpan = TimeSpan.FromSeconds(3)
    Property CheckProperties As Boolean = True
    Property Control As ItemsControl
    Dim Timer As Threading.Timer = New Threading.Timer(Sub() TimerTick(), Nothing, 0, 600)
    Dim _lastRefresh As Date?
    Dim Query As Func(Of IQueryable)
    Dim workingon As Date?

    Sub New(Query As Func(Of IQueryable), Control As ItemsControl)
        Me.Control = Control
        Me.Query = Query
    End Sub

    Async Sub TimerTick()
        Try
            If Now - _lastRefresh.GetValueOrDefault < RefreshSpan Then Exit Sub
            If GetLastInputTime() > 60 * 15 Then Exit Sub
            Dim isvis = False
            Await Control.Dispatcher.BeginInvoke(Sub() isvis = Control.IsUserVisible())
            If Not isvis Then Exit Sub
            If workingon.HasValue AndAlso workingon.Value > Now.AddSeconds(-15) Then Exit Sub 'if wasnt working for 15 seconds, probaly err or something
            workingon = Now
            Dim fq = Query.Invoke
            Dim itmtype = fq.ElementType
            Dim props = itmtype.CachedProperties.Where(Function(x) x.CanWrite AndAlso x.IsScalar(True)).ToList
            Dim keyprops = itmtype.CachedKeyProperties.ToList
            Dim newData = fq.ToObjectList
            If newData Is Nothing Then Exit Sub
            Dim keySelector As Func(Of Object, Object)
            Dim diff As CollectionDiff(Of Object)
            If itmtype.IsScalar Then 'list of strings..
                keySelector = Function(x) x
            Else
                If keyprops.Count <> 1 Then DevError("?")
                Dim kp = keyprops.FirstOrDefault
                keySelector = Function(x) kp.GetValue(x)
            End If
            diff = CollectionDiff(Me, newData, keySelector, props, CheckProperties)
            Dim toPreserve As Object
            ExecIfType(Of Primitives.Selector)(Control, Sub(x) toPreserve = x.Dispatcher.Invoke(Function() x.SelectedItem))
            If toPreserve IsNot Nothing Then diff.ToPreserve = {toPreserve}.ToDictionary(Function(x) x, Function(x) Nothing)
            diff.PreserveOnDelete = True
            If diff.ModificationCount > 400 Or diff.ClearOld Then
                CheckReentrancy()
                If diff.ClearOld Then
                    Items.Clear()
                Else
                    For Each pair In diff.ToReplaceByIndex
                        Control.Dispatcher.Invoke(Sub() Items(pair.Key) = pair.Value)
                    Next
                    For Each idx In diff.GetIndexesToDelete
                        Items.RemoveAt(idx)
                    Next
                End If
                For Each itm In diff.ToAdd 'for mem optimization im not using addrange
                    Items.Add(itm)
                Next
                MyBase.OnPropertyChanged(New PropertyChangedEventArgs("Count"))
                OnPropertyChanged(New PropertyChangedEventArgs("Items[]"))
                Control.Dispatcher.Invoke(Sub() OnCollectionChanged(New NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)))
            Else
                Dim preservIdx = diff.ToPreserve?.Select(Function(x) Items.IndexOf(x.Key))?.ToHashSet
                For Each pair In diff.ToReplaceByIndex
                    Control.Dispatcher.Invoke(Sub() Me(pair.Key) = pair.Value)
                Next
                For Each idx In diff.GetIndexesToDelete
                    If diff.PreserveOnDelete AndAlso preservIdx IsNot Nothing AndAlso preservIdx.Contains(idx) Then Continue For
                    Control.Dispatcher.Invoke(Sub() RemoveAt(idx))
                Next
                'don't use addrange - will cause a reset
                Await Control.Dispatcher.BeginInvoke(Sub() diff.ToAdd.ForEach(Sub(x) Add(x)))
            End If
            _lastRefresh = Now
            workingon = Nothing
            Control.Dispatcher.Invoke(Sub()
                                          Dim cvs = System.Windows.Data.CollectionViewSource.GetDefaultView(Me)
                                          If cvs.SortDescriptions.None Then
                                              Dim defsorts = {KVP("Name", False), KVP(NameOf(RecordBase.LastEditedOn), True), KVP(NameOf(LiteRecordBase.ID), True)}
                                              For Each defsort In defsorts
                                                  If itmtype.HasProperty(defsort.Key) Then
                                                      cvs.SortDescriptions.Add(New SortDescription(defsort.Key, If(defsort.Value, ListSortDirection.Descending, ListSortDirection.Ascending)))
                                                      Exit For
                                                  End If
                                              Next
                                          End If
                                      End Sub)
            RaiseEvent Refreshed(Me, Nothing)
        Catch ex As Exception
            Control.Dispatcher.BeginInvoke(Sub() ex.Rethrow)
        End Try
    End Sub
End Class