observablecollection predicate filter - powershell

Question

I would like to know how to filter the collection $view using a predicate filter. I have seen numerous examples of a predicate filter in C# but not many for PowerShell. It would be great to see a working example in PowerShell.
Basically when I set the filter variable to a string and refresh $view, the collection should filter to show me just the rows or objects that matched the filter. If the filter is empty the entire collection of objects should be shown.
I think this should work in the console without using any forms but i haven't been able to create a filter of the type (system.predicate) in PowerShell.
$a = New-Object System.Collections.ObjectModel.ObservableCollection[object]
$svcs = gsv -ComputerName LocalHost |
select #{n="Server";e={$_.machinename}},Name,Displayname,status
$svcs | ForEach {
$a.Add((
New-Object PSObject -Property #{
Server = $_.server
Name = $_.name
Displayname = $_.displayname
Status = $_.status
}
))
}
$view = [System.Windows.Data.CollectionViewSource]::GetDefaultView($a)
$filter = "bits"
$view.Filter = "Predicate FIlter???"
$view.Refresh()

Answer 1

Just pass a script block which takes a single parameter. The script block should return true for items which you want to include in the view and false for those that you do not want to include. The following works for me on PowerShell v4:
$view = [System.Windows.Data.CollectionViewSource]::GetDefaultView($a)
Write-Host "Setting filter to 'vss'"
$filter = "vss"
$view.Filter = {param ($item) $item -match $filter}
$view.Refresh()
$view
Write-Host "Setting filter to 'BITS'"
$filter = "BITS"
$view.Refresh()
$view
EDIT: Adding the output printed on a test computer of mine
Running the above script on a test computer resulted in the following output:
Setting filter to 'vss'
Status Server Name Displayname
------ ------ ---- -----------
Running LocalHost SQLWriter SQL Server VSS Writer
Stopped LocalHost vmicvss Hyper-V Volume Shado...
Stopped LocalHost VSS Volume Shadow Copy
Setting filter to 'BITS'
Running LocalHost BITS Background Intellige...