How to Find Duplicate Values in a PowerShell Custom Object ArrayList

Discover how to efficiently find and group duplicate values in a PowerShell ArrayList of custom objects using simple and effective methods.
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Understanding the Challenge: Finding Duplicate Values in a PowerShell ArrayList

If you're working with PowerShell and have created an ArrayList filled with custom objects, you may find yourself in a situation where you need to identify duplicates based on a specific property. For instance, let's say you have a collection of backup job records stored in an ArrayList and you want to find all instances where the "Jobname" is the same for multiple records.

The typical approach using Group-Object can lead to confusion since it aggregates all properties rather than focusing on the one you specified. This can leave you feeling frustrated, especially if you're not fully sure about how to structure or handle your ArrayList correctly.

In this guide, we'll break down a straightforward solution to find and display duplicate values based on the "Jobname" property.

Solution Overview

We'll tackle this problem by making a few improvements to the existing code structure:

Use Script-Scoping: Move from using global variables to script-scope, which is a more effective way of handling the variable scope.

Simplify Object Creation: Instead of utilizing multiple Add-Member commands to create objects, we'll leverage PowerShell's PsCustomObject for cleaner code.

Identify Duplicates: Use a grouping technique to find and format duplicates efficiently.

Step 1: Change Global Scope to Script Scope

Changing the variable definition from global: to script: helps to manage variable accessibility more effectively, which is essential for keeping your code clean and understandable. You should only reference the variable inside the function where it's needed.

Step 2: Simplify Object Creation

Instead of multiple Add-Member calls, we can streamline our object creation by directly using a hash table with the PsCustomObject. This reduces the lines of code and makes the object construction clearer.

Here's how to implement these ideas:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Populate the ArrayList

You can add multiple records by calling your AddBackupJobFoldertoArray function, like so:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Find Duplicate Jobnames

Now, we can easily find and display duplicates based on the "Jobname" property using a combination of Group-Object and filtering:

[[See Video to Reveal this Text or Code Snippet]]

This command groups the objects by their Jobname and filters those groups to show only those with more than one occurrence, neatly formatting them into a table.

Output Example

The output will show all duplicate job records, similar to the following:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following this structured approach, you can effectively manage and analyze data stored in a PowerShell ArrayList. The use of script-scope variables, simplified object creation, and effective grouping techniques streamlines your code and improves readability.

If you have further questions or need assistance with more advanced PowerShell functions, feel free to reach out or leave a comment below!