Question:
I have a Powershell script which gets a list of Remote Desktop user sessions and puts them into a hash by SessionID.
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# Create a hashtable which contains all of the remote desktop sessions by SessionId $userSessionBySessionID = @{} ForEach($userSession in Get-RDUserSession -CollectionName $collectionName) { $userSessionBySessionID.Add($userSession.SessionId, $userSession) } |
I then can then dump the $userSessionByID in the PowerShell ISE
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Name Value ---- ----- 9 Microsoft.RemoteDesktopServices.Management.RDUserSession 8 Microsoft.RemoteDesktopServices.Management.RDUserSession 7 Microsoft.RemoteDesktopServices.Management.RDUserSession 6 Microsoft.RemoteDesktopServices.Management.RDUserSession 5 Microsoft.RemoteDesktopServices.Management.RDUserSession 4 Microsoft.RemoteDesktopServices.Management.RDUserSession 2 Microsoft.RemoteDesktopServices.Management.RDUserSession 1 Microsoft.RemoteDesktopServices.Management.RDUserSession |
The frustrating part is that $userSessionBySessionID.ContainsKey(4) returns false. What am I missing here? I’ve tried $userSessionBySessionID.ContainsKey(“4”) as well, but that also returns false.
Answer:
I think the issue may be that
$userSession.SessionId.GetType()returns[UInt32]
In testing that is your issue exactly. Consider the following test where I create a hashtable using [UInt32].
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$test = @{} 1..10 | %{$test.add($_ -as [uint32],$_%2)} |
Running $test.containskey(6) returns false as you have seen. I also get the same issue with $test.containskey("6"). However this returns true….
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$test.containskey(6 -as [uint32]) |
Note: You don’t need to use the -as operator here as you can just do a simple cast with [uint32]6 however if you are using variables that contain integers -as would be helpful.
The key itself can be near any object and containskey() is returning the correct result in all cases. Your hashtable does not have a key with the integer 6. Furthermore, [uint32] cannot be converted to [int] since it has a higher upper bound so a cast would not be possible. This would be a reason why PowerShell or the underlying .Net would not be doing an “automatic” cast. In practice I don’t think this ever happens in this scenario.
Point is be sure you are type aware.
Same example as above except this time we are using integers.
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1..10 | %{$test.add($_,$_%2)} $test.containskey(6) True $test.containskey("6") False |
I can reverse the findings when I create the keys with strings.
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1..10 | %{$test.add("$_",$_%2)} $test.containskey(6) False $test.containskey("6") True |