FIX: A NullReferenceException exception occurs when you run a .NET Framework 4.0-based WPF application that has events in a nested template

SYMPTOMS
Consider the following scenario:
  • You have a Microsoft .NET Framework 4.0-based Windows Presentation Foundation (WPF) application.
  • In the application, there is one template that is nested inside another template.
  • The inner (nested) template contains a control that specifies a style and an event. The style references a static resource.

    For example, the XAML file of the WPF application resembles the following:
    <Grid>      <ListBox ItemsSource="{StaticResource Data}" >            <ListBox.ItemTemplate>                <DataTemplate>                    <ListBox ItemsSource="{Binding .}">                        <ListBox.ItemTemplate>                            <DataTemplate>                                <TextBlock Text="{Binding .}" Width="30"                                         Loaded="TextBlock_Loaded"                                         Style="{StaticResource TextBlockStyle}" />                            </DataTemplate>                        </ListBox.ItemTemplate>                    </ListBox>                </DataTemplate>            </ListBox.ItemTemplate>      </ListBox>  </Grid>
  • You run the WPF application.
In this scenario, a NullReferenceException exception occurs in the IStyleConnector.Connect method, and then the WPF application crashes.
CAUSE
This issue occurs because the inner template is quoted when the outer template is applied. When the application calls the IStyleConnector.Connect method, the instance of the control in the inner template is not available. Therefore, a NullReferenceException exception occurs.
RESOLUTION

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

To download this hotfix from the MSDN Code Gallery, visit the following Microsoft website:Note The MSDN Code Gallery displays the languages for which the hotfix is available. If you do not see your language listed, it is because the Code Gallery resource page is not available for that language.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website:Note You can also download this hotfix from the following Microsoft website:

Prerequisites

To apply this hotfix, you must have the Microsoft .NET Framework 4.0 installed.

Restart requirement

You may have to restart the computer after you apply the hotfix.
We recommend that you close all .NET Framework applications that lock or use the affected files before you install this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfix.

File Information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
For all supported x86-based versions of Windows XP, of Windows Server 2003, of Windows Vista, of Windows Server 2008, and of Windows 7
File nameFile versionFile sizeDateTimePlatform
Presentationframework.dll4.0.30319.3966,347,11225-Nov-201004:29x86
For all supported x64-based versions of Windows XP, of Windows Server 2003, of Windows Vista, of Windows Server 2008, of Windows 7, and of Windows Server 2008 R2
File nameFile versionFile sizeDateTimePlatform
Presentationframework.dll4.0.30319.3966,347,11225-Nov-201004:29x86

STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
WORKAROUND
To work around this issue, use one of the following methods:
  • Set the style reference to a dynamic resource.
  • Set the inner template as a resource for the outer template, and then remove the nest relationship.

Properties

Article ID: 2464222 - Last Review: 03/22/2011 08:39:00 - Revision: 2.0

Microsoft .NET Framework 4

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