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我有一个性能非常差的树控件,我正在尝试跟踪问题的根源。
我正在尝试确定以下警告是否重要:
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=ContextMenu.IsOpen; DataItem=null; target element is 'MultipleSelectionTreeViewItem' (Name=''); target property is 'NoTarget' (type 'Object')
DataContext
设置了显式绑定(bind)使用值(value)转换器尝试查看发生了什么。
<HierarchicalDataTemplate x:Key="HierarchyItemTemplate"
DataType="{x:Type local:HierarchyItem}"
ItemsSource="{Binding Children}">
<StackPanel DataContext="{Binding Converter={StaticResource DbgConverter}}" Orientation="Horizontal">
...
</StackPanel>
</HierarchicalDataTemplate>
System.Windows.ResourceDictionary Warning: 9 : Resource not found; ResourceKey='Img_Folder_Closed_Ex'
System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 41 : BindingExpression path error: 'IsFolder' property not found for 'object' because data item is null. This could happen because the data provider has not produced any data yet. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 20 :System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.ResourceDictionary Warning: 9 : Resource not found; ResourceKey='Img_QA'
System.Windows.Data Information: 41 : BindingExpression path error: 'IsIncluded' property not found for 'object' because data item is null. This could happen because the data provider has not produced any data yet. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=IsFolder; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 41 : BindingExpression path error: 'IsIncluded' property not found for 'object' because data item is null. This could happen because the data provider has noSystem.Windows.Data Information: 20 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
t produced any data yet. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 20 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarget' (type 'Object')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=IsIncluded; DataItem=null; target element is 'TreeViewItemIcon' (Name=''); target property is 'NoTarSystem.Windows.ResourceDictionary Warning: 9 : Resource not found; ResourceKey='Img_QA'
System.Windows.Data Information: 41 : BindingExpression path error: 'Name' property not found for 'object' because data item is null. This could happen because the data provider has not produced any data yet. BindingExpression:Path=Name; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 20 : BindingExpression cannot retrieve value due to missing information. BindingExpression:Path=Name; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 21 : BindingExpression cannot retrieve value from null data item. This could happen when binding is detached or when binding to a Nullable type that has no value. BindingExpression:Path=Name; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Name; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
get' (type 'Object')
<Application x:Class="ObservableCollectionTest.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
<Style x:Key="{x:Type TreeViewItem}" TargetType="{x:Type TreeViewItem}">
<Setter Property="HorizontalContentAlignment" Value="Left" />
<Setter Property="VerticalContentAlignment" Value="Center" />
</Style>
</Application.Resources>
</Application>
<Window x:Class="ObservableCollectionTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:l="clr-namespace:ObservableCollectionTest"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/ObservableCollectionTest;component/Theme.xaml" />
</ResourceDictionary.MergedDictionaries>
<l:Model x:Key="TheModel" />
</ResourceDictionary>
</Window.Resources>
<Grid>
<Grid.Resources>
<ObjectDataProvider x:Key="TheModelProvider" ObjectInstance="{StaticResource TheModel}" />
<HierarchicalDataTemplate
x:Key="TheModelTemplate"
DataType="{x:Type l:TestItem}"
ItemsSource="{Binding Items}">
<StackPanel Orientation="Horizontal">
<Image Style="{DynamicResource ImageStyle}" />
<Label>
<TextBlock Style="{DynamicResource TextBlockStyle}" Text="{Binding Name}" />
</Label>
</StackPanel>
</HierarchicalDataTemplate>
</Grid.Resources>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TreeView
ItemsSource="{Binding Source={StaticResource TheModelProvider}, Path=Items}"
ItemTemplate="{StaticResource TheModelTemplate}"/>
<Button
Grid.Row="1"
Height="30"
Content="Empty the list"
Click="EmptyTheList_Click" />
</Grid>
</Window>
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace ObservableCollectionTest
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
PresentationTraceSources.DataBindingSource.Listeners.Add(
new ConsoleTraceListener());
PresentationTraceSources.DataBindingSource.Switch.Level = SourceLevels.All;
InitializeComponent();
}
private void EmptyTheList_Click(object sender, RoutedEventArgs e)
{
(Resources["TheModel"] as Model).Items.Clear();
}
}
}
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
namespace ObservableCollectionTest
{
class Model
{
public ObservableCollection<TestItem> Items { get; set; }
public Model()
{
Items = new ObservableCollection<TestItem>()
{
new TestItem()
{
Name = "TopLevel",
Items = new List<TestItem>()
{
new TestItem() { Name = "Item1", Items = new List<TestItem>() },
new TestItem()
{
Name = "Item2",
Items = new List<TestItem>()
{
new TestItem() { Name = "SubItem1", Items = new List<TestItem>() },
new TestItem() { Name = "SubItem2", Items = new List<TestItem>() },
new TestItem() { Name = "SubItem3", Items = new List<TestItem>() }
}
},
new TestItem() { Name = "Item3", Items = new List<TestItem>() },
new TestItem() { Name = "Item4", Items = new List<TestItem>() }
}
}
};
}
}
class TestItem
{
public string Name { get; set; }
public bool IsRoot { get { return Name == "TopLevel"; } }
public List<TestItem> Items { get; set; }
}
}
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/ObservableCollectionTest;component/Common.xaml" />
</ResourceDictionary.MergedDictionaries>
<BitmapImage x:Key="Img_Folder_Open_In" UriSource="/ObservableCollectionTest;component/VS11_Light_Folder_Open_In.png" />
<BitmapImage x:Key="Img_Folder_Closed_In" UriSource="/ObservableCollectionTest;component/VS11_Light_Folder_Closed_In.png" />
</ResourceDictionary>
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style x:Key="TextBlockStyle" TargetType="TextBlock">
<Setter Property="Foreground" Value="Blue" />
<Setter Property="Background" Value="Yellow" />
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding Name}" Value="TopLevel" />
<Condition Binding="{Binding IsExpanded, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type TreeViewItem}}, FallbackValue=False}" Value="True" />
</MultiDataTrigger.Conditions>
<Setter Property="Background" Value="Red" />
</MultiDataTrigger>
</Style.Triggers>
</Style>
<Style x:Key="ImageStyle" TargetType="{x:Type Image}">
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding IsRoot}" Value="False" />
<Condition Binding="{Binding IsExpanded, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type TreeViewItem}}, FallbackValue=False}" Value="True" />
</MultiDataTrigger.Conditions>
<Setter Property="Source" Value="{DynamicResource Img_Folder_Open_In}" />
</MultiDataTrigger>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding IsRoot}" Value="False" />
<Condition Binding="{Binding IsExpanded, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type TreeViewItem}}, FallbackValue=False}" Value="False" />
</MultiDataTrigger.Conditions>
<Setter Property="Source" Value="{DynamicResource Img_Folder_Closed_In}" />
</MultiDataTrigger>
</Style.Triggers>
</Style>
</ResourceDictionary>
ObjectDataProvider
使用动态资源:
<ObjectDataProvider x:Key="TheModelProvider" ObjectInstance="{DynamicResource TheModel}" />
最佳答案
我已经设法摆脱了所有的绑定(bind)错误!
我不知道为什么,但将资源添加到 Application.Resources
而不是使用 UserControl.Resources
解决了Resource not found
错误。这远不是一个理想的解决方案(将用户控制资源的范围限定为用户控制会更好),但它确实有效。
所有其他dataItem=null
类型错误可以通过在各种绑定(bind)中提供回退值来解决。
这已经解决了引发这个问题的性能问题,所以我原来的问题的答案是 修复绑定(bind)错误确实会对性能产生很大影响 .现在我已经修复了绑定(bind),我的树更新几乎是即时的,而不是占用一秒钟 :)
非常感谢您的帮助!
杰里米
关于WPF 性能缓慢 - 许多 DataItem=null 绑定(bind)警告,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17492359/
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