PowerShell - modify a property in an array

calendar Jul 11, 2023 · 2 min read · powershell  ·
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We have a PowerShell dataset where we want to modify the values of a property but we don’t want to add a new property.

Imagine we want to convert the data like this, modifying one property so all the values are upper case but everything else is unchanged:

1Name   Age MyProperty        Name   Age MyProperty
2----   --- ----------        ----   --- -------------------
3Hugh    37 abc123      ----> Hugh    37 ABC123
4Pugh    24 ABCdef      ----> Pugh    24 ABCDEF
5Barney  21 GHIjkL      ----> Barney  21 GHIJKL

Let’s define this example data to work through a solution:

1$dataset=@(
2  [PSCustomObject]@{ Name = 'Hugh'; Age =37; MyProperty = 'abc123' }, `
3  [PSCustomObject]@{ Name = 'Pugh'; Age =24; MyProperty = 'ABCdef' }, `
4  [PSCustomObject]@{ Name = 'Barney'; Age =21; MyProperty = 'GHIjkL' } `
5)

Our initial dataset therefore looks like this:

1$dataset
2
3Name   Age MyProperty
4----   --- ----------
5Hugh    37 abc123
6Pugh    24 ABCdef
7Barney  21 GHIjkL

We can add a new property with MyProperty converted into upper-case quite easily using this PowerShell. We’re selecting all the properties with * and then adding a new property with the upper-cased value of each item.

1$dataset | Select-Object *, @{Name="MyUpperCaseProperty";Expression={$_.MyProperty.toUpper()}}
2
3Name   Age MyProperty MyUpperCaseProperty
4----   --- ---------- -------------------
5Hugh    37 abc123     ABC123
6Pugh    24 ABCdef     ABCDEF
7Barney  21 GHIjkL     GHIJKL

But we want to replace the values in MyProperty, not add a new one. If we try to overwrite it by calling our replacement property MyProperty we get an error.

1$dataset | Select-object *, @{Name="MyProperty";Expression={$_.MyProperty.toUpper()}}
2Select-Object: The property cannot be processed because the property "MyProperty" already exists.

The solution is to exclude the original MyProperty using the ExcludeProperty parameter of Select-Object like this:

1$dataset | Select-Object *, @{Name="MyProperty";Expression={$_.MyProperty.toUpper()}} -ExcludeProperty MyProperty
2
3Name   Age MyProperty
4----   --- ----------
5Hugh    37 ABC123
6Pugh    24 ABCDEF
7Barney  21 GHIJKL

And remember, we can also put this result back into our $dataset variable:

1$dataset= $dataset | Select-Object *, @{Name="MyProperty";Expression={$_.MyProperty.toUpper()}} -ExcludeProperty MyProperty