我在ScrollViewer中有一个ItemsControl。 ItemsControl.ItemSource设置为Observable Collection。
每次我将一个项目添加到集合中时，我的应用程序几乎会在内存使用量上增加一倍，并且最终会在添加足够的内容之后。
这是一个草图：
<Scrollviewer Name="MyScroll">
<ItemsControl Name="MyItemsControl">
.....standard itemscontrol code here, using <StackPanel> as presenter (VirtualizingStackPanel did not change my problem, btw)
.........
..DataTemplate has three textboxes and a textblock
</ItemsControl>
Code:
Class MyScroll
Dim myOBSCol as ObservableCollection(StudyUnit) 'studyunit is the core object of my application
'just holds a series of text properties as Dependency Properties
Sub New()
'create studyunit objects
For x as integer = 0 to 50
Dim SU as new StudyUnit
'.then I Set studyunit properties (i.e. Su.Text = "...", Su.IDNum = "2", etc...)
OBSCol.add(SU)
Next
MyItemsControl.ItemsSource=myOBSCol
End Sub
End Class
（请原谅我无法重现我的确切代码。我的代码编译都很好）
使用ANTS Memory Profiler，我可以看到我的应用程序中的所有类实例。当我启动程序时，我有150个TextBox实例（datatemplate中有三个）。当我将一个研究单元添加到该集合中时，我有303.添加另一个留给我456 ... 609 ......等。
studyunit对象继承自依赖项对象，我只绑定其依赖项属性。由于本文http://support.microsoft.com/kb/938416，我将研究单元作为一系列依赖属性，但它没有修复任何内容。
糟糕！
2010年2月22日更新。这是实际代码（上面的代码非常简化并且是从内存中创建的）
Private Sub ObservableCollectionChanged(ByVal sender As Object, ByVal e As System.Collections.Specialized.NotifyCollectionChangedEventArgs)
If e.Action = NotifyCollectionChangedAction.Remove Then 'q removed
Dim oldDict As IList = e.OldItems
If Not TryCast(oldDict(0), studyUnit) Is Nothing Then
Try
Catch ex As Exception
End Try
Else
End If
ElseIf e.Action = NotifyCollectionChangedAction.Add Then 'q added
'FIND ITEM IN LIST WITH NEW ITEM ID
Dim newQ As studyUnit
newQ = e.NewItems(0)
'set the location to provide focus after the new question is added
focusIndex = _ObsCol.getObjPosition(newQ)
Console.WriteLine("fi" + focusIndex.ToString)
ElseIf e.Action = NotifyCollectionChangedAction.Reset Then 'list "reset"
'call function that gives focus to the new control. (didn't affect memory issue when commented out'
giveFocus(focusIndex)
End If
'用于创建新StudyUnit并添加到ObservableCollection的代码
Private Sub addNewQuestion（ByVal location as eInsertQuestion，ByRef sender As TextBox） '通过按Enter键创建新问题的业务规则 '“新问题”文本框，您希望新问题出现
Dim sentText As TextBox = sender
'get qid of sender from "tag" object of the sender textbox
Dim senderQID As String = CInt(sentText.Tag)
'find this 'sender' question in the existing observable collection
Dim senderQuestion As studyUnit
For Each su As studyUnit In _ObsCol
If su.QID = senderQID Then
senderQuestion = su
Exit For
End If
Next
Dim newQuestionSortOrder As Integer
If location = eInsertQuestion.Before Then
newQuestionSortOrder = CInt(senderQuestion.sortOrder) 'will take over the sortorder of the previous question
ElseIf location = eInsertQuestion.After Then
'insert new question before
newQuestionSortOrder = CInt(senderQuestion.sortOrder) + 1
End If
'create the new question
Dim newQ As New studyUnit
'new "sort order"
newQ.sortOrder = CStr(newQuestionSortOrder)
'new "displayed order"
newQ.displayedOrder = generateNewQuestionDisplayedOrder(senderQuestion.displayedOrder) 'create a random question # for the new quesiton
'set HID to the sender's HID
newQ.HID = CStr(senderQuestion.HID)
'set type to "Question" //possibly not needed
'newQ.Add("suType", eSUnitType.Question)
'now send this studyunit to the database (then we can get its QID in the database)
My.Application.dComm.insertQuestion(newQ)
'set "NEW Q" = the exact data inserted in the database (as a best practice)
newQ = Nothing
newQ = My.Application.dComm.getNewestQuestionStudyUnit()
'AddHandler newQ.studyUnitChangedEvent, AddressOf StudyUnitAltered
'add to main question collection...
'find position of sender question
Dim senderIndex As Integer = Me._ObsCol.getObjPosition(senderQuestion)
Dim newLocation As Integer = senderIndex + location '("location" will be equal to +1 (after) or 0 (before)
'insert before or after that one
If newLocation < _ObsCol.Count Then
_ObsCol.Insert(newLocation, newQ)
Else
_ObsCol.Add(newQ) 'can't "insert" if index is greater than the current size of the collection, use add function instead
End If
For x As Integer = newLocation + 1 To _ObsCol.Count - 1 'obscol is zero-based
Dim thisQ As studyUnit = CType(_ObsCol(x), studyUnit)
If thisQ.suType = eSUnitType.Question Then
'increase each question's sort order by 1
thisQ.sortOrder = CStr(CInt(thisQ.sortOrder) + 1)
Else
'else: do nothing, this study unit is a heading or section, does not get a change in sortOrder
End If
Next
'以下是对问题的一个很好的解释 '我尝试重置itemsource，但是DataTemplate实例不会从内存中清除......即使第三行被注释掉了。 itemscontrol将变为空，但所有datatemplate对象都保留在内存中。
Me.SP_ItemsControl.ItemsSource = Nothing
Me.SP_ItemsControl.Items.Clear()
Me.SP_ItemsControl.ItemsSource = _ObsCol
End Sub
'以下是我的数据表。这些是由DataTemplateSelector选择的：
<local:BindableRTBConverter x:Key="RTBConverter" />
<local:ColorConverter x:Key="myColorConverter"/>
<local:HeadingsNameConverter x:Key="myHeadingConverter"/>
<!-- Styles that can be used throughout all three datatemplates here-->
<Style x:Key="borderStyleSettings" TargetType="Border">
<Setter Property="Border.Margin" Value="5,5,5,5"/>
<Setter Property="Border.BorderBrush" Value="{Binding Source={StaticResource ApplicationUserSettings}, Path=borderColor, Converter={StaticResource myColorConverter}}" />
<Setter Property="Border.BorderThickness" Value=".9"/>
<Setter Property="Border.CornerRadius" Value="6"/>
</Style>
<Style x:Key="textStyleSettings" TargetType="TextBlock">
<Setter Property="TextBlock.FontSize" Value="{Binding Source={StaticResource ApplicationUserSettings}, Path=fontSize}" />
<Setter Property="TextBlock.TextWrapping" Value="Wrap" />
<Setter Property="TextBlock.VerticalAlignment" Value="Center"/>
</Style>
<!--end of styles-->
<!--Section RN Template-->
<DataTemplate x:Key="RNSectionTemplate">
<DataTemplate.Resources>
</DataTemplate.Resources>
<Border Tag="{Binding Path=SID, Mode=OneTime}" Style="{StaticResource borderStyleSettings}">
<StackPanel>
<TextBlock Margin="3,3,3,0" Foreground="Black" FontStyle="Italic" FontWeight="Bold" HorizontalAlignment="Center" Style="{StaticResource textStyleSettings}">
<TextBlock.Text>
<MultiBinding Converter="{StaticResource myHeadingConverter}"
ConverterParameter="getRNSectionTitle" Mode="OneWay">
<Binding Path="num"/>
<Binding Path="name"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</StackPanel>
</Border>
</DataTemplate>
<!--Heading RN Template-->
<DataTemplate x:Key="RNHeadingTemplate">
<DataTemplate.Resources>
</DataTemplate.Resources>
<Border Tag="{Binding Path=HID, Mode=OneTime}" Style="{StaticResource borderStyleSettings}">
<StackPanel>
<TextBlock Margin="3,3,3,0" Foreground="Black" FontWeight="Bold" HorizontalAlignment="Left" Style="{StaticResource textStyleSettings}">
<TextBlock.Text>
<MultiBinding Converter="{StaticResource myHeadingConverter}"
ConverterParameter="getRNHeadingTitle" Mode="OneWay">
<Binding Path="num"/>
<Binding Path="name"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</StackPanel>
</Border>
</DataTemplate>
<!--Question RN Template-->
<DataTemplate x:Key="RNQuestionTemplate">
<DataTemplate.Resources>
<Style TargetType="local:BindableRTB">
<Setter Property="FontSize" Value="15"/>
<Setter Property="HorizontalAlignment" Value="Left"/>
<Setter Property="Foreground" Value="Black"/>
<Setter Property="FontFamily" Value="{Binding Source={StaticResource ApplicationUserSettings}, Path=fontName}"/>
<Setter Property="Template">
<Setter.Value>
<!--Sets changes container of textbox control from ScrollViewer to Adorner Decorator, as an attempt to
reduce the memory waste in "scrollbar" instances. Didn't help much. Also didn't impact my memory leak.-->
<ControlTemplate TargetType="{x:Type TextBoxBase}">
<Border
Name="Border"
CornerRadius="0"
Padding="0"
Background="White"
BorderThickness="0"
>
<AdornerDecorator Margin="0" x:Name="PART_ContentHost"></AdornerDecorator>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="TextBox">
<Setter Property="FontSize" Value="15"/>
<Setter Property="BorderThickness" Value="3"/>
<Setter Property="FontFamily" Value="{Binding Source={StaticResource ApplicationUserSettings}, Path=fontName}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBoxBase}">
<Border
Name="Border"
CornerRadius="0"
Padding="0"
Background="White"
BorderThickness="0"
>
<AdornerDecorator Margin="0" x:Name="PART_ContentHost"></AdornerDecorator>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="TextBlock">
<Style.Setters>
<Setter Property="Foreground" Value="Purple"></Setter>
<Setter Property="FontFamily" Value="{Binding Source={StaticResource ApplicationUserSettings}, Path=fontName}"/>
</Style.Setters>
</Style>
</DataTemplate.Resources>
<!-- Main border -->
<Border Style="{StaticResource borderStyleSettings}">
<Grid Name="myStack" HorizontalAlignment="Stretch" Margin="4" Tag="{Binding Path=QID, Mode=OneTime}">
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
<!-- last column for controls to be added later, if wanted-->
</Grid.ColumnDefinitions>
<!--Row 0-->
<!-- Displayed Order textbox (editable) -->
<TextBox Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="1" IsTabStop="False" BorderThickness="0">
<TextBox.Text>
<Binding Path="displayedOrder" Mode="TwoWay" UpdateSourceTrigger="LostFocus"/>
</TextBox.Text>
</TextBox>
<!-- delete button -->
<Ellipse Grid.Column="2" Grid.Row="0" Tag="{Binding Path=QID, Mode=OneTime}" Name="ellipseDelete" Height="12" Width="12" Stroke="Black"
Fill="LightGray" Stretch="Fill" HorizontalAlignment="Right"></Ellipse>
<!-- Row 1 -->
<!-- Main text area -->
<local:BindableRTB Name="myRTB" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2">
<local:BindableRTB.Document>
<Binding Converter="{StaticResource RTBConverter}" Path="Question" Mode="TwoWay" UpdateSourceTrigger="LostFocus"/>
</local:BindableRTB.Document>
</local:BindableRTB>
<!--Page Ref-->
<TextBox Name="txtPageRef" Grid.Column="2" Grid.Row="1" Grid.ColumnSpan="1" IsTabStop="False">
<TextBox.Text>
<Binding Path="pageRef" Mode="TwoWay" UpdateSourceTrigger="LostFocus"/>
</TextBox.Text>
</TextBox>
<!-- Row 2 -->
<!-- New question textbox -->
<StackPanel Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="3" HorizontalAlignment="Stretch">
<StackPanel.Style>
<Style TargetType="StackPanel">
<Style.Setters>
<Setter Property="Background" Value="Transparent" />
</Style.Setters>
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter Property="Background" Value="LightGreen"/>
</Trigger>
</Style.Triggers>
</Style>
</StackPanel.Style>
<!-- Binding the questions "QID" to the 'new quesiton' textbox. For the bubbling keydown event,
This information can help determine where to insert the new question, and then give focus
to that new question-->
<TextBox Name="newQuestionTextBox" Tag="{Binding Path=QID, Mode=OneTime}" Background="Transparent" IsReadOnly="True" BorderThickness="0" FontSize="10" HorizontalAlignment="Left">
<TextBox.Style>
<Style TargetType="TextBox">
<Style.Triggers>
<Trigger Property="IsKeyboardFocused" Value="True">
<Setter Property="FontStyle" Value="Italic"/>
<Setter Property="Text" Value="(Start typing to create a new question. Press the ALT key to insert a new question above.)"/>
</Trigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
</StackPanel>
<!-- Endof New question textbox -->
</Grid>
</Border>
</DataTemplate>
<!--End of reviewnote Templates-->
数据模板选择器
导入System.Windows.Controls 进口System.Windows 公共类typeDataTemplateSelector 继承DataTemplateSelector
Public Overrides Function SelectTemplate(ByVal item As Object, ByVal container As System.Windows.DependencyObject) As System.Windows.DataTemplate
Dim sUnit As studyUnit = DirectCast(item, studyUnit)
Dim mainWindow As R2_CoreWindow = CType(My.Application.MainWindow, R2_CoreWindow)
If sUnit.suType = eSUnitType.Heading Then
Return mainWindow.WpfEditor.FindResource("RNHeadingTemplate")
ElseIf sUnit.suType = eSUnitType.Section Then
Return mainWindow.WpfEditor.FindResource("RNSectionTemplate")
ElseIf sUnit.suType = eSUnitType.Question Then
Return mainWindow.WpfEditor.FindResource("RNQuestionTemplate")
End If
End Function
结束班
'ItemsControl XAML
<!-- Scrollviewer_Keydown is looking for bubbling keydown event from New Quesitons-->
<ScrollViewer.Resources>
<!-- Template selector for each Data Template -->
<local:typeDataTemplateSelector x:Key="myTempSelector"></local:typeDataTemplateSelector>
</ScrollViewer.Resources>
<ItemsControl Name="SP_ItemsControl" ItemTemplateSelector="{StaticResource myTempSelector}">
<!--Set the itemssource in code later-->
<ItemsControl.Template>
<ControlTemplate TargetType="ItemsControl">
<ItemsPresenter/>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel></StackPanel>
<!-- Use of virtualizingstackpanel didn't help -->
<!--<VirtualizingStackPanel VirtualizingStackPanel.IsVirtualizing="True" VirtualizingStackPanel.VirtualizationMode="Recycling" />-->
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
StudyUnit（浓缩......对于15+差异属性重复同样的事情）
Public Class studyUnit 继承DependencyObject
Public Property Question() As String
Get
Return GetValue(QuestionProperty)
End Get
Set(ByVal value As String)
SetValue(QuestionProperty, value)
End Set
End Property
Public Shared QuestionProperty As DependencyProperty = DependencyProperty.Register("Question", GetType(String), _
GetType(DependencyObject), New PropertyMetadata(Nothing, New PropertyChangedCallback(AddressOf OnQuestionPropertyChanged)))
Private Shared Sub OnQuestionPropertyChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
'目前没有使用此回调...会在此处放置代码与我的数据库通信，这是我的内容的原始来源 结束子 '所有其他属性都完全像上面那样设置
答案 0 :(得分：2)
更好！
问题在于将我的observable集合绑定到ItemsControl的ItemsSource属性。
无论出于何种原因（也许有人可以解释这一点），每次我将项目添加到可观察集合时，ItemsControl都必须重新创建列表中的所有项目。这导致非常不规则的记忆问题（有时加倍，慢慢增加，甚至随着每个项目的增加而减少）。
由于我的要求，我能够接受手动管理Items集合的不太优雅的解决方案。 （我能够保持每个项目与studyunit对象的绑定没有问题，这是我的应用程序的核心需求。
要强制更改ObservableCollection以更新UI，我只需要添加此代码（我只显示了添加单个项目所需的代码）：
Private Sub obscolchanged(ByVal sender As Object, ByVal e As System.Collections.Specialized.NotifyCollectionChangedEventArgs)
If e.Action = NotifyCollectionChangedAction.Add Then 'q added
Dim newSU As studyUnit
newSU = e.NewItems(0)
dim newIndex as Integer = _ObsCol.IndexOf(newSU)
If newIndex < Me.ItemsControl.Items.Count
Me.ItemsControl.Items.Insert(newIndex, newSU)
Else
'when newSU is the last item, simply add to the end of the collection, or you will get an IndexOutOfRange exception
Me.ItemsControl.Items.Add(newSU)
End If
End If
End Sub
可以编写类似的代码来处理移动事件和删除事件。这显然不如使用ItemsSource属性那么方便，但我没有遇到内存问题，并且添加项目的速度要快得多，因为ItemsControl在更改Collection时不必重新生成每个DataTemplate。
谢谢你，ItemsControl，当我缩短30分钟时吸收近40个小时：）
答案 1 :(得分：0)
问题在于框架，将itemsource更改为datagrid或datagridview并且所有工作正常且更快