InstallDotNetCustomExtension.tf

  extension {
    name                       = "InstallDotNet"
    publisher                  = "Microsoft.Compute"
    type                       = "CustomScriptExtension"
    type_handler_version       = "1.8"
    auto_upgrade_minor_version = true
    settings                   = <<EOF
    {
      "fileUris": [
        "https://yourblobstorageaccount.blob.core.windows.net/dotnet48/InstallDotNet-48.ps1"
      ],
      "commandToExecute": "powershell -ExecutionPolicy Unrestricted -File InstallDotNet-48.ps1"
    }
    EOF
  }