I already figured out how to use UrlDecode in PowerShell:
PS Z:\> Add-Type -AssemblyName System.Web
PS Z:\> [System.Web.HttpUtility]::UrlDecode("First+Line%0D%0ASecond+Line ")
I also figured out that I can load System.Web by adding corresponding command to "C:\Windows\System32\WindowsPowerShell\v1.0\profile.ps1" so I don't have to do this manually each time I open PowerShell.
However, I still have to type [System.Web.HttpUtility]::UrlDecode each time which is a hassle even when using tab to auto-complete.
Is there a way to create an alias so that instead of
[System.Web.HttpUtility]::UrlDecode("First+Line%0D%0ASecond+Line")
I can just type
urdc("First+Line%0D%0ASecond+Line")
or better yet
urdc "First+Line%0D%0ASecond+Line"
?