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A hotfix is available for the ASP.NET browser definition files in the .NET Framework 3.5.1

View products that this article applies to.


This article describes a hotfix for the ASP.NET browser definition files that are included in the Microsoft .NET Framework 3.5.1.

Note These ASP.NET browser definition files are part of the Microsoft .NET Framework 3.5.1 that is included in the release to manufacturer (RTM) version of Windows 7 and of Windows Server 2008 R2.

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More Information

This hotfix introduces updated definitions in the browser definition file for Internet Explorer. The browser definition files are stored in one of the following folders, depending on the installed version of the Microsoft .NET Framework:
  • For 32-bit versions of the .NET Framework 3.5.1

  • For 64-bit versions of the .NET Framework 3.5.1

By default, ASP.NET uses sniffing technology for the user agent string to detect browsers. The browser definition files cover a certain range of browser versions. However, as the version numbers increase, ASP.NET might not recognize new versions of a browser by using the user agent string. In this case, ASP.NET might handle these versions as an unknown browser. For example, ASP.NET cannot recognize Windows Internet Explorer 10 that has the following user agent string:

Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. 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.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

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 The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must have the .NET Framework 3.5.1 installed.

Restart information

After you apply this hotfix, you might have to restart the computer if any affected files are being used when you install this hotfix.

To avoid a restart of the computer, shut down all web server applications for ASP.NET websites before you apply this hotfix.

Replacement information

This hotfix does not replace a previously-released 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 the .NET Framework 3.5.1
File nameFile versionFile sizeDateTimePlatform
Ie.browserNot Applicable18,41131-Aug-201100:17Not Applicable
For all supported x64-based versions of the .NET Framework 3.5.1
File nameFile versionFile sizeDateTimePlatform
Ie.browserNot Applicable18,41131-Aug-201100:16Not Applicable
Note Because of file dependencies, this hotfix might also contain other files.

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Common issue that occurs without this hotfix

Consider the following scenario:
  • You use Windows Internet Explorer 10 to access an ASP.NET-based webpage.
  • The webpage starts a postback.

In this scenario, the postback fails, and you receive the following error message:
Script Error encountered", "'__doPostBack' is undefined

Note The webpage can start a postback in various ways. For example, a LinkButton control can start a postback.

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The hotfix that applies to the ASP.NET files in the Microsoft .NET Framework 2.0 Service Pack 2 (SP2) and in the Microsoft .NET Framework 3.5 Service Pack 1 (SP1) is hotfix 2600100.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:
2600100 A hotfix is available for the ASP.NET browser definition files in the .NET Framework 2.0 SP2 and in the .NET Framework 3.5 SP1
For more information about the browser definition file schema, visit the following Microsoft website:
For more information about the Internet Explorer 10 user agent string, visit the following Microsoft website:
For more information about how to detect Internet Explorer more effectively, visit the following Microsoft website:

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Keywords: kbautohotfix, kbqfe, kbhotfixserver, kbfix, kbsurveynew, kbexpertiseadvanced, kb

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Article Info
Article ID : 2608565
Revision : 2
Created on : 9/29/2018
Published on : 9/29/2018
Exists online : False
Views : 166