Updates NuGet in Visual Studio 2015. Assumes you installed Visual Studio 2015 to the default path.

UpdateNuget.ps1

function IsVisualStudioRunning {
    Try {
	    $visualStudioInstances = (Get-Process devenv)
        return ($visualStudioInstances.Length -gt 0)
    }
    Catch {
        return $false
    }
}

function RemoveExistingExtensionFoldersContainingNuGet {
	Write-Output 'Removing old installations of NuGet...'	
	$extensionsDir = "$env:ProgramFiles\Microsoft Visual Studio 14.0\Common7\IDE\Extensions"
    Get-ChildItem -Recurse $extensionsDir -Include "NuGet.VisualStudio.Implementation.dll" | Select -ExpandProperty Directory | Remove-Item -Recurse -Force
}

function DownloadAndInstallNugetExtension {
	Write-Output 'Downloading latest distribution of NuGet for Visual Studio 2015...'
	$source = 'https://dist.nuget.org/visualstudio-2015-vsix/latest/NuGet.Tools.vsix'
	$temp = [System.IO.Path]::GetTempPath()
	$destination = (Join-Path $temp 'NuGet.Tools.vsix')
	Invoke-WebRequest $source -OutFile $destination
	
	Write-Output 'Installing NuGet...'
    & "$env:ProgramFiles\Microsoft Visual Studio 14.0\Common7\IDE\VSIXInstaller" /q $destination
}

function Main {
	if (IsVisualStudioRunning) {
        Write-Error 'Please close all instances of Visual Studio before proceeding.  I would kill them for you but I probably don''t have permission.'
        return
    }
    
	RemoveExistingExtensionFoldersContainingNuGet
	DownloadAndInstallNugetExtension
}

Main