Why won’t Variable update?

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tl;dr

In order to update the $BaseHomeFolderPath variable in the script scope (or any scope other than the local one), you must reference it in that scope explicitly:

$script:BaseHomeFolderPath="\\path1\users"

Otherwise, without a scope specifier such as $script:, you’ll implicitly create a new variable by that name in the current scope, which in your case is the child scope in which your event handlers run.

In PowerShell, when you assign to a variable with $var = ..., you either:

  • update a preexisting variable that was created in the same scope.

  • or implicitly create a new variable in the current scope.

The tricky part is that even though child scopes see variables created in parent scopes and can get their value by name only, assigning to them by name only creates a new, scope-local variable, and that new variable then shadows the original one in the current scope and all child scopes.

A simple demonstration, using call operator & to execute a script block ({ ... }) in a child scope:

$var="parent"
"in parent: before: $var"
& {
  "in child: before: $var" # sees $var from parent scope 
  $var="child"           # creates new $var in current scope
  "in child: after: $var"  # sees new $var, which shadows the parent's
}
"in parent: after: $var"   # still has original value

This prints:

in parent: before: parent
in child: before: parent
in child: after: child
in parent: after: parent

Note:

  • The behavior also applies to the implicit assignment that occurs with the ++ and -- operators (given that, e.g., ++$var is the same as $var += 1)

    • See this answer for an example of where this can constitute a pitfall.

  • In addition to fixed-target scope specifiers $script: and $global:, you can use the Get-Variable / Set-Variable cmdlets with the -Scope parameter to target variables in scopes relative to the current one (up the call stack; e.g., -Scope 1 refers to the parent scope).

  • To promote modularity and maintainability, it’s generally better to avoid accessing variables across scope boundaries – best to pass values around instead.

For more information, see:

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