Ajax not working (Installed Microsoft.jQuery.....)

Hi All, is anyone have idea why Ajax seems not recognized even if I installed Nuget packages microsoft.jquery.Unobtrusive.Ajax and microsoft.jquery.Unobtrusive.Validation,

when I typed Ajax. in my cshtml file it has the red underline?

Thanks in advance.Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.