Powershell - return custom object to C# host
a) define the variable to the runtime first with
run.SessionStateProxy.SetVariable("result", null)
b) maybe could help to mark $result as global (not verified):
$global:result = New-Object TheLibrary.ScriptResult
GetVariable returns a PSVariable instance. The variable's value is in the .Value property. You'll probably need to cast it (DirectCast) to your ScriptResult type as Value returns an Object.