Errors in Visual Studio register.aspx file

[Bluenose]

Hello

I am getting the following compilation error in my register.aspx file:

C30456: 'GetOwinContext' is not a member of 'System.Web.HttpContext'.

This is my code:

 Protected Sub CreateUser_Click(sender As Object, e As EventArgs)
        Dim userName As String = Email.Text
        Dim manager = Context.GetOwinContext().GetUserManager(Of ApplicationUserManager)()
        Dim signInManager = Context.GetOwinContext().Get(Of ApplicationSignInManager)()
        Dim user = New ApplicationUser() With {.userName = userName, .Email = userName}
        Dim result = manager.Create(user, Password.Text)
        If result.Succeeded Then
            ' For more information on how to enable account confirmation and password reset please visit http://go.microsoft.com/fwlink/?LinkID=320771
            ' Dim code = manager.GenerateEmailConfirmationToken(user.Id)
            ' Dim callbackUrl = IdentityHelper.GetUserConfirmationRedirectUrl(code, user.Id, Request)
            ' manager.SendEmail(user.Id, "Confirm your account", "Please confirm your account by clicking <a href=""" & callbackUrl & """>here</a>.")
 
            signInManager.SignIn(user, isPersistent:=False, rememberBrowser:=False)
            IdentityHelper.RedirectToReturnUrl(Request.QueryString("ReturnUrl"), Response)
        Else
            ErrorMessage.Text = result.Errors.FirstOrDefault()
        End If
    End Sub

The following, from the above code, are underlined in red:

Context.GetOwinContext

Error: Not a member of httpContext

IdentityHelper

Error: it is not declared.

At the top of my file, the following are underlined in VS 2017 in green as not being necessary:

Imports Microsoft.AspNet.Identity
Imports Microsoft.AspNet.Identity.EntityFramework
Imports Microsoft.AspNet.Identity.Owin
Imports Owin

Where do I go from here, please?

Thanks!

[SioSio]

Are you writing like this?
Dim Context As HttpContext

If so, it will look like
Context.Current.GetOwinContext