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The performance of a WPF application that contains many visual elements becomes slow when a UI Automation client application is running

Article ID: 978520 - View products that this article applies to.

SYMPTOMS

Consider the following scenario:

You have a Microsoft .NET Framework 3.5 Service Pack 1 (SP1)-based Windows Presentation Foundation (WPF) application that contains many visual elements.
You run the application on one of the following computers:
- A touch-enabled computer on which a Tablet PC Input Panel Accessory (TabTip.exe) process is running by default. For example, you run the application on a tablet computer.
- A computer on which a User Interface (UI) Automation client application is running. Examples of UI Automation applications include Narrator, Magnifier, and UI Spy.
You interact with the WPF application. For example, you scroll within the application.

In this scenario, the performance of the WPF application becomes slow. The CPU usage increases, or the application responds slowly.

Note The problem does not occur in the .NET Framework 4.0.

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This issue occurs because Accessibility clients must collect UI Automation information to interact with applications. This behavior causes WPF to start UI Automation events at the end of each layout. However, WPF checks every element in the application to determine whether to start an automation event. Therefore, the performance becomes slower, depending on the performance of the computer and on the number of elements in the WPF application.

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RESOLUTION

Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, use one of the following methods.

Method 1

Download this hotfix from the following MSDN Code Gallery Web site:

http://code.msdn.microsoft.com/KB978520

(http://code.msdn.microsoft.com/KB978520)

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.

Method 2

Download this hotfix rollup from the following Microsoft Connect Web site:

http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=27829

(http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=27829)

Method 3

Contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

(http://support.microsoft.com/contactus/?ws=support)

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

This hotfix is scheduled to be included in the .NET Framework 4.0.

Prerequisites

You must have the .NET Framework 3.5 SP1 installed to apply this hotfix.

Restart requirement

You do not have to restart the computer after you apply the hotfix if affected files are not being used.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

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.