Why Does PowerShell Complain It Can't Retrieve a Variable?

July 19, 2023

I’m getting the following error message:

The variable '$dateTime' cannot be retrieved because it has not been set.

The error is generated by the line [DateTime]$dateTime in this code:

  [string]$registryEntry = Read-Registry -path $SCRIPT_KEY -name $key

   [DateTime]$dateTime 
   if ($null -ne $registryEntry) {
      $dateTime = [DateTime]$registryEntry
   }
   return $dateTime

But the error message makes no sense: I’m not trying to retrieve the $dateTime variable, I’m just declaring it.

I have to return a DateTime object, or $null if it’s undefined. FYI, the registry entry is the string “19 Jul 2023 05:52”

How do I make this work?

$psVersionTable:

Name                           Value
----                           -----
PSVersion                      7.3.6
PSEdition                      Core
GitCommitId                    7.3.6
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

>Solution :

As the error very clearly states:

because it has not been set.

PowerShell doesn’t really have a concept of "variable declaration" – if you want to strongly type a variable, you’ll have to do it as part of an assignment operation – which in turn will solve your problem:

[string]$registryEntry = Read-Registry -path $SCRIPT_KEY -name $key

[datetime]$dateTime = [datetime]::MinValue
if ($null -ne $registryEntry) {
    $dateTime = [DateTime]$registryEntry
}

return $dateTime