asp.net String not retained on postback

I am trying to create the following scenario...

• A user logs in by inserting their user id and password.
• If they don't have an email address assigned to their login details they are asked to submit one before they can continue.
• They then continue to the home page in a logged in state.

The trouble I'm having is that the user id and password are not retained when they submit their email address so the login fails.

Here's the code...

Dim userid as String
Dim password as String

Sub Page_Load(ByVal Sender as Object, ByVal E as EventArgs)

end sub


Sub Page_Transfer()

Dim userLookup As mySource.myData = New mySource.myData()
Dim drSet1 As DataSet = userLookup.xyz("SELECT * FROM OPENQUERY (myDatabase,' SELECT userid, password, email1 FROM userInfo WHERE userid = ''" & userid & "'' AND password = ''" & password & "'' ') ")

If drSet1.Tables(0).Rows.Count < 1 Then
    'Invalid Bond number
    Page.ClientScript.RegisterClientScriptInclude("loginError", "scripts/loginError.js")
Else

        If drSet1.Tables(0).Rows(0).Item("email1") = "" Then
            'No email address
            Page.ClientScript.RegisterClientScriptInclude("emailAddressSubmit", "scripts/emailAddressSubmit.js")
        Else

            response.redirect("home.aspx")

        End If

End If

End Sub


Sub Submit_Email(sender As Object, e As System.Web.UI.ImageClickEventArgs)

'script to add email address to开发者_StackOverflow database
'this is where the strings are losing their values

Page_Transfer()

End Sub


Sub Submit_login(sender As Object, e As System.Web.UI.ImageClickEventArgs)

userid = Trim(useridfield.text)
password = Trim(passwordfield.text)

Page_Transfer()

End Sub

Any ideas?

The problem is that, with every postback, the page goes through a full new lifecycle. That means that any instance variables of your page which you set during one postback are lost in the next one.

How to solve this problem? You have the following options:

1. Read userid and password again from the controls (useridfield and passwordfield). Since ASP.NET controls use the view state to retain their values after postback, the value in these controls should still be valid.

2. Use the view state yourself to save the variable's values, i.e., replace

   Dim userid as String 
   Dim password as String 
   

   with

   Protected Property userid As String
       Get
           Return DirectCast(Me.ViewState("userid"), String)
       End Get
       Set
           Me.ViewState("userid") = value
       End Set
   End Property
   ' same for password
   

   Be aware, though, that the view state is not secure, i.e., it can be modified by a skilled user of your web application. Thus, be sure to validate the values of userid and password again (check the DB to see if they match) before assigning a mail address to them. (Same holds for option 1, by the way.)

3. Save the values somewhere else, for example, in the Session.