I tried to add a test, but I cannot find a way to get the EventHandler methods from the event member AppDomain.ProcessExit ...

I can get the invocation method list in .NET, but not in .NET Core. The following works in Windows PowerShell

$f = [System.AppDomain].GetFields([System.Reflection.BindingFlags]::Instance -bor [System.Reflection.BindingFlags]::NonPublic -bor [System.Reflection.BindingFlags]::GetField) | ? name -eq '_processExit'
$v = $f.GetValue([System.AppDomain]::CurrentDomain)
$v.GetInvocationList()

Method                                                          Target
------                                                          ------
Void DisposeOnShutdown(System.Object, System.EventArgs)
Void CurrentDomain_ProcessExit(System.Object, System.EventArgs)
Void SingletonDomainUnload(System.Object, System.EventArgs)     {System.EventHandler}

So at least I can add a test when porting this change to Windows PowerShell.

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@daxian-dbw I got it ("static" is key):

$f = [System.AppContext].GetFields([System.Reflection.BindingFlags]::Instance -bor [System.Reflection.BindingFlags]::NonPublic -bor [System.Reflection.BindingFlags]::GetProperty -bor [System.Reflection.BindingFlags]::Static) | ? name -eq 'ProcessExit'
$v = $f.GetValue([System.AppDomain]::CurrentDomain)
# or $f.GetValue([System.AppContext]::ProcessExit)

$v.GetInvocationList()

@iSazonov This is very strange, and feels to me may randomly stop working in future .NET Core 😄

@daxian-dbw AppContext is public API and the property is static - it is not likely that this public API will be changed.

Ahh, I thought it was [System.AppDomain]. Just realized you were using [System.AppContext].

$f.GetValue([System.AppDomain]::CurrentDomain)

This is wrong, should pass in $null as argument. I will submit a test for this change then.

Hmm, I cannot write a Pester test for this, because the leak won't happen as long as a Runspace still opens. Need to do it in xUnit.

This is wrong, should pass in $null as argument.

I don't understand your thought. It seem works well in the example I posted.

It's a static field, so should pass null when calling GetValue. Your code works but that may be because the dotnet implementation just ignored the passed in argument, which could change to check for null in future.

Sorry, if I noisy but I always wonder how in-depth you look.
Do you mean that [System.AppDomain]::CurrentDomain can be null? I see it is non-nullable and initialized with new AppDomain().
Also we can use $f.GetValue([System.AppContext]::ProcessExit) as I mentioned in example above.

I was not clear in my above statement. Today, you can pass anything to $f.GetValue() when it's a static field. For example:

PS:32> $f = [System.AppContext].GetFields([System.Reflection.BindingFlags]::NonPublic -bor [System.Reflection.BindingFlags]::GetProperty -bor [System.Reflection.BindingFlags]::Static) | ? name -eq 'ProcessExit'
PS:33> $f.GetValue("fff")

Target Method
------ ------
       Void CurrentDomain_ProcessExit(System.Object, System.EventArgs)

It may be because today the .net implementation ignore the argument when the field is static, but this could change in future so that exception would be thrown if the passed in argument is not null.

Thanks for clarify!
It would be a breaking change which is incredible for dotnet runtime.

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