How does Select-Object stop the pipeline in PowerShell v3?

Question

In PowerShell v2, the following line:

1..3| foreach { Write-Host \"Value : $_\"; $_ }| select -First 1

Would display:

Value         


        

Answer 1

Check this post on how you can cancel a pipeline:
http://powershell.com/cs/blogs/tobias/archive/2010/01/01/cancelling-a-pipeline.aspx

In PowerShell 3.0 it's an engine improvement. From the CTP1 samples folder ('\Engines Demos\Misc\ConnectBugFixes.ps1'):

# Connect Bug 332685
# Select-Object optimization
# Submitted by Shay Levi
# Connect Suggestion 286219
# PSV2: Lazy pipeline - ability for cmdlets to say "NO MORE"
# Submitted by Karl Prosser

# Stop the pipeline once the objects have been selected
# Useful for commands that return a lot of objects, like dealing with the event log

# In PS 2.0, this took a long time even though we only wanted the first 10 events
Start-Process powershell.exe -Args '-Version 2 -NoExit -Command Get-WinEvent | Select-Object -First 10'

# In PS 3.0, the pipeline stops after retrieving the first 10 objects
Get-WinEvent | Select-Object -First 10