具有自定义窗口样式的后台STA线程使用窗口镶边抛出交叉线程访问异常 [英] Background STA thread with custom window style using window chrome throwing cross threaded access exception
问题描述
这个有点奇怪. 从wpf的主窗口(单击按钮)，我正在创建另一个STA Thread，其中显示了自定义窗口.该自定义窗口的样式使用的是Shell中的WindowChrome类. 调用Show()方法时出现异常.
This one is bit bizarre. From a main window in wpf (on a button click), I am creating another STA Thread where I am showing a custom window. This custom window is applied with a style that uses the WindowChrome class from shell. I get an exception while calling the Show() method.
无法跨以下站点访问Freezable'System.Windows.Shell.WindowChrome' 线程，因为它无法冻结.
Cannot access Freezable 'System.Windows.Shell.WindowChrome' across threads because it cannot be frozen.
如果我删除WindowChrome安装程序，则一切正常. 我想念什么?
If I remove the WindowChrome setter, everything works just fine. What am I missing?
我已经尝试过将窗口镀铬标记为冻结，但是徒劳！
I've already tried marking the window chrome as frozen, but in vain!
在此处可获得源代码的副本.
A copy of the source is available here.
更新: 忘记提及在样式上添加x:Shared ="False"似乎可以解决问题，但我不知道为什么！这会导致性能瓶颈吗?
Update: Forgot to mention that adding x:Shared="False" on the style seems to fix the problem, but I do not know why! Will this cause any performance bottlenecks?
MainWindow.xaml:
<Window x:Class="WpfApplication7.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication7"
Title="MainWindow"
Height="350"
Width="525" Style="{StaticResource ResourceKey=WindowStyle}">
<Grid>
<Button Content="Open another window please..."
Click="Button_Click" />
</Grid>
</Window>
MainWindow.xaml.cs:
using System.Threading;
using System.Windows;
namespace WpfApplication7
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Thread windowThread = new Thread(new ThreadStart(() =>
{
Window customWindow = new BackgroundWindow();
customWindow.Closed += (s, a) => System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvokeShutdown(System.Windows.Threading.DispatcherPriority.Background);
customWindow.Show();
System.Windows.Threading.Dispatcher.Run();
}));
windowThread.IsBackground = true;
windowThread.SetApartmentState(ApartmentState.STA);
windowThread.Start();
}
}
}
BackgroundWindow.xaml:
<Window x:Class="WpfApplication7.BackgroundWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication7"
Title="BackgroundWindow"
WindowStartupLocation="CenterScreen"
Style="{StaticResource ResourceKey=WindowStyle}">
</Window>
WindowStyle.xaml(与App.xaml合并
<!-- Setting x:Shared=False will solve the cross threaded exception -->
<Style x:Key="WindowStyle"
TargetType="{x:Type Window}">
<Setter Property="Padding"
Value="5,5,5,5" />
<Setter Property="BorderBrush"
Value="Black" />
<Setter Property="BorderThickness"
Value="1" />
<Setter Property="WindowChrome.WindowChrome">
<Setter.Value>
<WindowChrome CaptionHeight="44"
GlassFrameThickness="-1"
CornerRadius="0,0,0,0" />
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Window}">
<Border Background="{TemplateBinding Property=Background}"
BorderBrush="{TemplateBinding Property=BorderBrush}"
BorderThickness="{TemplateBinding Property=BorderThickness}">
<Grid Background="{TemplateBinding Property=Background}"
UseLayoutRounding="True"
SnapsToDevicePixels="True">
<Grid.RowDefinitions>
<!-- Window Controls -->
<RowDefinition Height="44" />
<!-- Content -->
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<DockPanel x:Name="PART_DragPanel"
Grid.Row="0"
Background="Black">
<Button x:Name="PART_CloseButton"
DockPanel.Dock="Right"
HorizontalAlignment="Right"
Margin="3,8,8,8"
WindowChrome.IsHitTestVisibleInChrome="True"
Width="20"
Height="20" />
<Button x:Name="PART_RestoreButton"
DockPanel.Dock="Right"
HorizontalAlignment="Right"
Margin="3,8,3,8"
Visibility="Collapsed"
WindowChrome.IsHitTestVisibleInChrome="True"
Width="20"
Height="20" />
<Button x:Name="PART_MinimizeButton"
DockPanel.Dock="Right"
HorizontalAlignment="Right"
Margin="3,8,3,8"
Visibility="Collapsed"
WindowChrome.IsHitTestVisibleInChrome="True"
Width="20"
Height="20" />
<TextBlock x:Name="PART_Title"
DockPanel.Dock="Left"
Margin="8,8,8,8"
Text="{TemplateBinding Property=Title}"
IsHitTestVisible="False"
WindowChrome.IsHitTestVisibleInChrome="True" />
</DockPanel>
<Border x:Name="contentBorder"
Grid.Row="1"
Padding="{TemplateBinding Property=Padding}">
<AdornerDecorator>
<ContentPresenter />
</AdornerDecorator>
</Border>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="ResizeMode"
Value="CanMinimize">
<Setter TargetName="PART_MinimizeButton"
Property="Visibility"
Value="Visible" />
</Trigger>
<Trigger Property="ResizeMode"
Value="NoResize">
<Setter TargetName="PART_RestoreButton"
Property="Visibility"
Value="Collapsed" />
<Setter TargetName="PART_MinimizeButton"
Property="Visibility"
Value="Collapsed" />
</Trigger>
<Trigger Property="ResizeMode"
Value="CanResize">
<Setter TargetName="PART_RestoreButton"
Property="Visibility"
Value="Visible" />
<Setter TargetName="PART_MinimizeButton"
Property="Visibility"
Value="Visible" />
</Trigger>
<Trigger Property="ResizeMode"
Value="CanResizeWithGrip">
<Setter TargetName="PART_RestoreButton"
Property="Visibility"
Value="Visible" />
<Setter TargetName="PART_MinimizeButton"
Property="Visibility"
Value="Visible" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="ResizeMode"
Value="CanResize">
<Setter Property="WindowChrome.ResizeBorderThickness"
Value="5,5,5,5" />
</Trigger>
<Trigger Property="ResizeMode"
Value="CanResizeWithGrip">
<Setter Property="WindowChrome.ResizeBorderThickness"
Value="5,5,5,5" />
</Trigger>
<Trigger Property="ResizeMode"
Value="NoResize">
<Setter Property="WindowChrome.ResizeBorderThickness"
Value="0,0,0,0" />
</Trigger>
</Style.Triggers>
</Style>
推荐答案
问题的根源是何时执行此操作:
The root of the problem is when you do this:
<Setter Property="WindowChrome.WindowChrome">
<Setter.Value>
<WindowChrome CaptionHeight="44"
GlassFrameThickness="-1"
CornerRadius="0,0,0,0" />
</Setter.Value>
</Setter>
值(在这种情况下为WindowChrome实例)仅创建一次，并在构造时保留样式.每次将样式应用于控件时，它都不会创建新实例.首先，您将样式应用于主窗口.此时，将通过xaml创建样式，因此将创建WindowChrome实例.当您从另一个线程将样式应用于背景窗口时-不重新创建样式，将使用已创建的Style实例.注意到样式设置器包含在另一个线程中创建的值，该值是可冻结的而不是冻结的，因此它会失败，因为它被认为是危险的(因为您无法分配在另一个线程中创建的WindowChrome实例，所以无论如何都不会起作用)到您的BackgroundWindow，也无法克隆它.)
The value (WindowChrome instance in this case) is created once and preserved in style when it is constructed. It will not create new instances each time style is applied to control. First you apply style to main window. At this point style is created from xaml, and so WindowChrome instance is created. When you apply style to background window from another thread - style is not recreated, already created instance of Style is used. It is being noticed that style setter contains value created in another thread, that value is freezable but not frozen - so it fails with exception, because it is considered dangerous (and will not work anyway because you cannot assign this WindowChrome instance created in another thread to your BackgroundWindow, nor can you clone it).
将x:Shared=False应用于样式时-在每个请求上创建Style的新实例，从而避免了该问题(因为也为Style的每个实例创建了WindowChrome的新实例).强制新约的另一种方法是:
When you apply x:Shared=False to style - new instance of Style is created on each request, avoiding the problem (because new instance of WindowChrome is created too for each instance of Style). Another way to force new intsance is:
<WindowChrome x:Key="chrome" x:Shared="False"
CaptionHeight="44"
GlassFrameThickness="-1"
CornerRadius="0,0,0,0" />
<Style ...>
<Setter Property="WindowChrome.WindowChrome" Value="{DynamicResource chrome}"/>
</Style>
仅在没有其他方法时才使用多个UI线程，因为它们可能很棘手.
Only use multiple UI threads when there is really no other way, because they might be tricky.
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