Get-TypeData

Exploring Get-TypeData in PowerShell

Welcome back to Wahmans PowerShell Blog! Today, we’re diving into a lesser-known but incredibly powerful cmdlet: Get-TypeData. If you’re curious about how PowerShell enhances the behavior of .NET types through extended type data, then you’re in for a treat!

What is Get-TypeData?

The Get-TypeData cmdlet retrieves the extended type data in your current session. Extended type data is what allows PowerShell to add custom properties, methods, or format views to existing .NET types or objects. This is part of PowerShell’s type extension mechanism and is primarily defined in .ps1xml files.

By querying extended type data, you can understand how PowerShell enhances objects under the hood, and even define your own custom type extensions using Update-TypeData or Import-LocalizedData.

Example 1: List All Extended Type Data (Beginner)

To see a full list of registered extended type data in your current session:

Get-TypeData

This returns an object for each extended type entry, showing you the type name, members added, and the origin of the data (e.g., user-defined or from PowerShell).

Example 2: Check Type Data for a Specific Type (Intermediate)

If you’re curious about how PowerShell extends a specific type, such as System.Diagnostics.Process:

Get-TypeData -TypeName System.Diagnostics.Process

This shows member additions like ScriptProperties and NoteProperties. These extensions make your PowerShell experience richer, such as by providing friendly alias properties.

Example 3: Show Only PowerShell-Defined Type Data (Intermediate)

You can filter the result to only show type data added by PowerShell default formatting files (not custom):

Get-TypeData | Where-Object { $_.IsPreTypeData -eq $true }

This is useful if you want to inspect only the built-in extensions and separate them from the ones you or a module have added during the session.

Example 4: Investigate Custom Type Data (Advanced)

Let’s assume you, or a module you imported, added a custom property to the System.String type. To inspect it:

Get-TypeData -TypeName System.String | Select-Object -ExpandProperty Members

This will list all the ScriptProperties, AliasProperties, and other members added to the System.String type by extended type data.

This is essential for debugging or understanding how modules may change or enhance your object outputs.

Wrapping Up

Get-TypeData is a fantastic tool for seeing what enhancements PowerShell makes to standard .NET objects. Whether you’re just browsing or actively developing custom extensions, this cmdlet should be in your toolkit.

Happy scripting, and I will see you in the next post!