PowerShell 2 and .NET Framework 4

By default PowerShell 2 is using .NET CLR 2.0.

It is quite annoying. I would like to be able to use something like [string]::IsNullOrWhitespace from .NET Framework 4

There are several approaches

1. Modify .NET settings globally saying to use only latest .NET CLR version

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework]
"OnlyUseLatestCLR"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework]
"OnlyUseLatestCLR"=dword:00000001

2. Modify or create the files powershell.exe.config and powershell_ise.exe.config in $PSHOME folder

<?xml version="1.0"?> 
<configuration> 
    <startup useLegacyV2RuntimeActivationPolicy="true"> 
        <supportedRuntime version="v4.0.30319"/> 
        <supportedRuntime version="v2.0.50727"/> 
    </startup> 
</configuration>

To check what you have use

# Current PowerShell version

$host.Version

# Current .NET Framework version

[Environment]::Version

Unfortunately both of these approaches did not work well if you have PowerShell 3 installed.

If you run PowerShell.exe -Version 2 it will run PowerShell version 2 with .NET version 2 If you use one of the approached shown above

$host.Version is always 3 even if you ran PowerShell.exe -Version 2.

EDIT: Raised a bug https://connect.microsoft.com/PowerShell/feedback/details/767907/powershell-2-0-with-net-4-0-on-windows-8