Install .Net 3.5 using DSC & Azure Blob

dotNetInstall-DSC.ps1

configuration DotNet3
{
    Import-DscResource -ModuleName xPSDesiredStateConfiguration

    node localhost
    {

        $dotNetSXSfolder = "C:\Installs\dotNetsxs"
        File dotNetSXSFolder
        {
            Type            = "directory"
            DestinationPath = $dotNetSXSfolder
            Ensure          = "Present"
        }

        xRemoteFile DotNet351SXS
        {
            Uri             = "https://xxxxxxxxxx.blob.core.windows.net/dotnet/2016/microsoft-windows-netfx3-ondemand-package.cab"
            DestinationPath = "$dotNetSXSfolder"
            DependsOn       = "[File]dotNetSXSFolder"
            MatchSource     = $false
        }

        WindowsFeature FriendlyName
        {
           Ensure = "Present"
           Name   = "NET-Framework-Core"
           Source = $dotNetSXSfolder
        }

    }
}

# Creates a mof and applies the resource
$DscDir = "C:\DSC\"
New-Item $DscDir -ItemType Directory -ErrorAction SilentlyContinue | Out-Null
DotNet3 -OutputPath $DscDir
Start-DscConfiguration -Path $DscDir -Wait -Force -Verbose

For those scenarios where you don't want to rely on a full copy of the Windows media.

This relies on copying the above .cab from the Windows media and making the blob publicly available.

Typically use a file share resource, blob was an experiment.