A NullReferenceException exception occurs when a TextBox control in a WPF-based application receives the focus in the .NET Framework 3.5

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Symptoms
You run a Windows Presentation Foundation (WPF)-based application on a computer that has Microsoft .NET Framework 3.5 installed. When a TextBox control of the application receives the focus, a NullReferenceException exception may occur that causes the application to crash.
Cause
This issue occurs because the Input Method Editor (IME) mode of the TextBox control enters a state that causes a NullReferenceException exception when it receives a notification from the TextBox control.

Note This notification is sent after the TextBox control receives the focus.
Resolution
To resolve this issue, apply the hotfix package that is described in the following Microsoft Knowledge Base article:

2667241 An update rollup is available for Windows Presentation Foundation (WPF) for Microsoft .NET Framework 3.5
Workaround
To work around this problem, turn off the advanced text services.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More information
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates
Properties

Article ID: 979562 - Last Review: 11/02/2013 21:51:00 - Revision: 5.0

  • Microsoft .NET Framework 3.5
  • kbnosurvey kbarchive kbexpertiseadvanced kbsurveynew kbqfe kbHotfixServer KB979562
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