The Microsoft Active Directory module for Windows PowerShell reveals a multi-threading issue.

This sample repository depicts that multi-threading issue.

When a number of PowerShell runspaces are created in several threads of a .NET Framework application, and if those PowerShell runspaces simultaneously run Cmdlets from the Microsoft Active Directory module for Windows PowerShell, then Active Directory Web Services (ADWS) fails by throwing an invalid enumration context exception of type System.ServiceModel.FaultException.

So, enumeration contexts don't seem to be stored thread-safe by Microsoft Active Directory module for Windows PowerShell.

• Make sure you have access to a Windows Active Directory domain controller from your development machine.

• .NET Framework 4.7.2 must be installed on the development machine for the project to compile.

• To create an executable file from the code in this repository, Microsoft Visual Studio 2017/2019 should be installed on the development machine.

1. Download this repository to your local drive on your development machine.
2. Open the PowerShell Test.sln file using Visual Studio 2017/2019.
3. Make sure to download the referenced System.Management.Automation.dll NuGet package using Visual Studio 2017/2019 Package Manager.
4. Compile and run the console application.

The code in this repository's project creates a number of threads that run in parallel.

Within each of these threads, a new PowerShell runspace is created and within each PowerShell runspace a PowerShell script is invoked. Basically, all threads simply invoke the same PowerShell script.

What the PowerShell script does is simply accessing Active Directory Web Services (ADWS) by querying LDAP a number of times, running the Get-ADUser Cmdlet from the Microsoft Active Directory module for Windows PowerShell.

Each of the LDAP queries establishes its own enumeration context when connecting to Active Directory Web Services. Yet, when iterating the result returned by Active Directory Web Services, wrong enumeration context information is sent to ADWS which results in a System.ServiceModel.FaultException to be thrown with the exception message invalid enumeration context.

There are many programmers out there facing the invalid enumeration context issue.

With this sample project the failure can easily be reproduced. Currently, there is no workaround for this issue.

I believe this to be a bug in Microsoft Active Directory module for Windows PowerShell. It is a breaking issue and I hope Microsoft will be able to fix it using the test code from this repository.