FIX: A System.ArgumentException exception occurs when you run a multithreaded .NET Framework 3.5-based application that calls classes in the System.DirectoryServices.AccountManagement namespace

Article translations Article translations
Article ID: 971595 - View products that this article applies to.
Expand all | Collapse all

On This Page


You have a multithreaded Microsoft .NET Framework 3.5-based application. This application calls classes in the System.DirectoryServices.AccountManagement namespace. When you run this application, an ArgumentException exception occurs. Addtionally, you receive the following message:
An item with the same key has already been added.


This problem occurs because a function internally caches property sets in a static dictionary variable. However, this function is not thread-safe.


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 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 Web site:
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.


You must have the .NET Framework 3.5 Service Pack 1 (SP1) installed to apply this hotfix.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace 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.
For all supported x86-based, x64-based, and Itanium-based versions of Windows Server 2000, of Windows XP, and of Windows Server 2003
Collapse this tableExpand this table
File nameFile versionFile sizeDateTimePlatform


To work around this problem, use the single-thread mode for the application.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Call stack information

at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
at System.DirectoryServices.AccountManagement.ADStoreCtx.BuildPropertySet(Type p, StringCollection propertySet)
at System.DirectoryServices.AccountManagement.ADStoreCtx.PushFilterToNativeSearcher(PrincipalSearcher ps)
at System.DirectoryServices.AccountManagement.ADStoreCtx.Query(PrincipalSearcher ps, Int32 sizeLimit)
at System.DirectoryServices.AccountManagement.PrincipalSearcher.FindAll(Boolean returnOne)
at System.DirectoryServices.AccountManagement.PrincipalSearcher.FindAll()


Article ID: 971595 - Last Review: October 7, 2011 - Revision: 2.0
  • Microsoft .NET Framework 3.5
  • Microsoft .NET Framework 3.5 Service Pack 1
kbexpertiseadvanced kbsurveynew kbqfe KB971595

Give Feedback


Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from