Understanding Why the Same Script Fails in C# While Working in Exchange Management Shell

Discover why PowerShell scripts that run perfectly in Exchange Management Shell 2010 don't work via C# , and learn how to resolve this common issue.
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Why Does the Same PowerShell Script Work in Exchange Management Shell 2010 but Not in C# ?

When working with PowerShell scripts in Exchange environments, developers and system administrators may encounter discrepancies between running scripts directly in the Exchange Management Shell and executing them through a C# application. In this guide, we will investigate a common scenario where a script that retrieves forwarding email addresses fails in C# , while it works perfectly in the Exchange shell.

The Problem

The PowerShell script in question aims to collect and process mailbox forwarding addresses. Here is a summary of its main functionality:

Retrieve all mailboxes without NULL forwarding addresses.

Add a member property for the contact address by fetching details from Active Directory.

Output the results in a format usable for C# code.

However, when attempting to run this script through C# , a frustrating exception occurs, indicating that an expected value, specifically Identity, is NULL. The main issue arises from the line of code responsible for extracting the DistinguishedName property from the $fwd.ForwardingAddress, which unexpectedly returns null in the C# context.

Understanding the Cause

Serialized Objects in Remote Sessions

When connecting to Exchange remotely using PowerShell, you work with serialized objects known as dehydrated or string-ified objects. Here’s why this matters:

Local Execution: In the Exchange Management Shell, objects are fully realized and maintain all their properties and methods. For instance, the ForwardingAddress property is of type [Microsoft.Exchange.Data.Directory.ADObjectId], which has a DistinguishedName attribute.

Remote Execution: When using a remote PowerShell session, the server returns a simplified version of these objects. Instead of the full fidelity objects, properties like ForwardingAddress appear as simple string representations (often a canonical name in string format).

The Root of the Problem

This difference in object representation leads to the core issue at hand. When the code is run locally, ForwardingAddress holds the necessary object and its properties, including DistinguishedName. Yet when streamed from a remote session, these properties are not available, resulting in a NULL value and the subsequent error when run through C# .

Solutions to the Problem

To address this challenge, consider the following solutions:

1. Develop in Matching Environments

The simplest way to avoid such confusion is to develop your code in the same environment where it will eventually be deployed. By mirroring the production environment in your development setup, you mitigate environment-specific discrepancies and retain full access to object methods.

2. Implement Conditional Logic for Object Types

If developing under identical conditions isn't feasible, you can incorporate logic into your code that checks the type of the objects returned. Below is an example of how you might implement this:

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This technique allows you to adapt your processing flow according to the type of object encountered, facilitating smoother operations in both remote and local environments.

Conclusion

Understanding the distinctions between how PowerShell handles objects locally versus remotely can significantly help troubleshoot and solve common scripting issues. Emphasizing the context of object types, as shown here, is essential for developing robust solutions that perform consistently across different environments.

Final Thoughts

Navigating the intricacies of PowerShell, especially within the Exchange management context, can be cha