Assists in updating an existing Sitecore Visual Studio solution to the new nuget structure for 9.1, when using packages.config style Nuget. This code is provided AS-IS, and is not supported by Sitecore.

ConvertToNewNuget-packagesconfig.ps1

## Nuget v2 URL for the target platform, and the target marketing version
$SitecoreNuget = "https://sitecore.myget.org/F/sc-platform-9-1/api/v2"
$TargetVersion = "9.1.0"

function Add-XMLAttribute([System.Xml.XmlNode] $Node, $Name, $Value)
{
  $attrib = $Node.OwnerDocument.CreateAttribute($Name)
  $attrib.Value = $Value
  $node.Attributes.Append($attrib)
}

## Nuget URL to retrieve package metadata, including dependencies
$MetaPackage = "$SitecoreNuget/Packages(Id='Sitecore.Experience.Platform',Version='$TargetVersion')"

## Retrieve the package metadata from nuget (no nice way of doing this via CLI)
$PackageMetadata = [xml](Invoke-WebRequest $MetaPackage).Content

## Parse the package dependencies so we know the appropriate package versions for this release
$versions = $PackageMetadata.entry.properties.Dependencies.Split('|') | % {
    $dependencySplit = $_.Split(':')
    New-Object PSObject -Property @{
        Name = $dependencySplit[0]
        Version = $dependencySplit[1]
    }
}

## Package folder may be at a different depth but should always contain this
$packageFolder = "..\packages\"
Get-ChildItem *.csproj -recurse | % {
    New-Object psobject -Property @{
        File = $_
        ProjectXml = [xml](gc $_ -Raw)
    }
} | % {
    $fileName = $_.File.Name

    ## Find the packages.config for the project    
    $packagesConfig = $_.File.Directory | Get-ChildItem | ? { $_.Name -eq "packages.config" } | select -first 1
    if (-not $packagesConfig) {
        Write-Host "WARNING: Could not find packages.config for $fileName" -ForegroundColor yellow
        return
    }
    $packagesConfigXml = [xml]($packagesConfig | gc -Raw)

    ## Use of packages.config means you'll have a regular Reference
    $_.ProjectXml.GetElementsByTagName("Reference") | ? {
        ## Ensure it's a Sitecore nuget reference, that's not FakeDb
        $_.HintPath -and $_.HintPath.Contains($packageFolder) -and $_.Include.StartsWith("Sitecore") -and -not $_.Include.Contains("FakeDb")
    } | % {
        ## Resolve the full path to the packages folder
        $packagesPath = $_.HintPath.Substring(0, $_.HintPath.IndexOf($packageFolder) + $packageFolder.Length)
        ## For Sitecore nuget, package name will be assembly name
        $packageName = $_.Include.Split(",")[0]
        ## Look up the appropriate version
        $newPackage = $versions | ? { $_.Name -eq $packageName } | select -first 1
        if (-not $newPackage) {
            Write-Host "WARNING: Could not find new version for package $packageName in $fileName" -ForegroundColor yellow
            return
        }
        ## Version will include pin markers, not needed here
        $numberVersion = $newPackage.Version.Replace("[", "").Replace("]", "")
        ## Update reference and path based on metadata lookup
        $_.Include = "$packageName" ## Would be difficult to determine assembly version, might differ from package
        $_.HintPath = "$($packagesPath)$($packageName).$numberVersion\lib\net471\$($packageName).dll"
        
        ## Find the package in packages.config, maybe with .NoReferences suffix
        $packageReference = $packagesConfigXml.packages.package | ? { $_.id -eq $packageName } | select -first 1
        if (-not $packageReference) {
            $packageReference = $packagesConfigXml.packages.package | ? { $_.id -eq "$packageName.NoReferences" } | select -first 1
        }
        if (-not $packageReference) {
            Write-Host "WARNING: Could not find $packageName in packages.config for $fileName" -ForegroundColor yellow
            return
        }

        ## Ensure package no longer uses .NoReferences
        $packageReference.id = $packageName
        $packageReference.version = $numberVersion
        if ($packageReference.allowedVersions) {
            $packageReference.allowedVersions = $newPackage.Version
        } else {
            Add-XMLAttribute -Node $packageReference -Name allowedVersions -Value $newPackage.Version | out-null
        }
        $packageReference.targetFramework = "net471"
    }

    ## Save the project file and packages.config
    $_.ProjectXml.Save($_.File)
    $packagesConfigXml.Save($packagesConfig.FullName)
}