Replace values in hashtable in PowerShell

Question

I have a hashtable in PowerShell that looks like this:

$table = @{
     1 =  3;
     2 =  3;
     5 =  6;
    10 = 12;
    30 =  3
}

I need to replace all "3" values with "4".

Is there a nice and clean way to do this without iterating over each pair and writing each one to a new hashtable?
Could the action with the same data be done easier if I'd use some other .NET collection class?

This throws exception that "Collection was modified":

$table.GetEnumerator() | ? {$_.Value -eq 3} | % { $table[$_.Key]=4 }

This adds another "Values" member to the object and breaks it:

$table.Values = $table.Values -replace 3,4

Possible duplicate of Powershell updating hash table values in a foreach loop?. — Peter Mortensen
– Peter Mortensen, Commented Jan 21, 2019 at 22:20

Duncan · Accepted Answer · 2014-02-04 11:47:52Z

2

You can't modify the table while iterating over it, so do the iteration first and then do the updates. Just split your pipeline in two:

PS>$change = $table.GetEnumerator() | ? {$_.Value -eq 3}
PS>$change | % { $table[$_.Key]=4 }
PS>$table

Name                           Value
----                           -----
30                             4
10                             12
5                              6
2                              4
1                              4

answered Feb 4, 2014 at 11:47

Duncan

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1 Comment

Roman Kuzmin Over a year ago

One liner: @($table.GetEnumerator()) | ? {$_.Value -eq 3} | % { $table[$_.Key]=4 }

Prid · Accepted Answer · 2023-08-08 22:20:17Z

0

The above answer didn't work for me and I couldn't fit this as a comment. The above single-lined answer didn't do anything. I am trying to change a single value to "Off" based on my hashtable.Key aka Name. Notice where I wrote $(backtick) is supposed to be a literal backtick, but it was messing up the code block. Here is my hashtable that is pulled from .\BeepVariables.txt.

Name                    Value
----                    ----
$varAwareCaseSound       "On"
$varEmailSound           "On"

function SetHash2([string]$keyword, [string]$value){
   $hash = @{}
   $hash = (get-content .\BeepVariables.txt).replace(";"," $(backtick) n") | ConvertFrom-StringData
   @($hash.GetEnumerator()) | ?{$_.key -like "*$keyword*"} | %{$hash[$_.value]=$value}
   $hash
}
SetHash2 "aware" '"Off"'

edited Aug 8, 2023 at 22:20

Prid

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answered Feb 1, 2020 at 22:44

Chris

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