Using Test-Path to find value item in hashtable - powershell

Question

I have recently started using Set-StrictMode to get into better scripting habbits (i.e. declaring variables and such) and I have run into a small issue. For most of my scripts I will create a hashtable $Script = #{} and then declare all variables used within the script as sub properties under that because no matter what, when you start the script, all the variables will be clean and if you print out all the variables at the end of your script you know they will be from that specific session.
Historically if I needed to see if a subvariable such as $Script.RunOnce was declared I would just use If ($Script.RunOnce) {} but with strict mode you have to do something along the lines of this If (Test-Path Variable:\Script.WriteOnce) {} except test-path sees "Script.WriteOnce" as its own variable, not a sub variables underneath $Script
Why do I need to do this you may ask? Well I am writing a function that uses .Net Streamwriter and I want to make sure that if the variable "$WriteTee.StreamWriter" exists run the $WriteTee.StreamWriter.Close and $WriteTee.StreamWriter.Flush prior to declaring $Write-Tee again or else when I attempt to open a new streamwriter it will error out and I have to manually close the .net handle on the file before I can continue testing the script.
Long story short
Is there a way to test for $WriteTee.StreamWriter using Test-Path or some other way that doesn't create an error with Set-Strictmode
Super gutted example verison of my script.
Set-StrictMode -Version Latest
$ErrorActionPreference = 'Inquire'
Function Write-Tee {
Begin {
#Variables that are needed only the first time the log function is started.
If ($WriteTee.RunOnce) {
If ($WriteTee.StreamWriter) { Write-Tee -Severity Error -Message "Log Writer Already Open. Attempting to close." -Close}
New-Variable -ErrorAction SilentlyContinue -Force -Name WriteTee -Value #{} -Scope Script
$Script:WriteTee.RunOnce = $True
}
}#End-Begin
Process {}#End-Process
End {
If ($Close -AND $Script:WriteTee) {
Write-Tee -Severity Info -Message "Flushing Log Writer and closing."
$WriteTee.StreamWriter.Flush()
$WriteTee.StreamWriter.Close()
Remove-Variable -ErrorAction SilentlyContinue -Force -Name WriteTee -Scope Script
Remove-Variable -ErrorAction SilentlyContinue -Force -Name WriteTee
}#End-If
}#End-End
}
Write-Tee -Message "Test" -Severity "Warning"

Answer 1

You can use test-path with the variable provider and the name of the variable to find out if a variable has been assigned to, but finding properties of a variable (or items in a hashtable, it's not clear which you are dealing with) requires other tactics:
To find out if a hashtable has an item with a key, you can do something like:
$writeTee.ContainsKey('StreamWriter') #returns $true or $false
To find out if a variable has a particular property, you can use get-member:
$writeTee | Get-Member -name StreamWriter #returns the member or nothing