How To Remember Form Values Without Postback

[Wee Bubba]

hello there.

 

i need to persist the form values of a particular web page so that if a user gets timed out then i can repopulate it when they return to that page. likewise, if a user fills half the form in then decides to browse a different page before returning later on, then i will also need to remember the values.

 

i dont believe that i can trap either of these events with a postback so at the moment i am thinking the best solution is to keep storing the form values inside a cookie every time the javascript 'onunload' event handler fires. i can then repopulate from the cookie when a user comes back to the page. i can enforce that cookies is on for users of my application as it has a private user base so thats not a problem. however ive heard that certain popup stopper applications block this event handler so its perhaps not the best way.

 

is there a better way?

[JTDPublix]

You could store each value in a cookie when each form element loses focus. I believe you could use the onBlur event to tell when the user has finished with the element and its lost focus.

[TheWizardofInt]

Create a class called globVars

 

Post this code into it:

 

Public Class globVars
#Region "Private Variables"
   Protected Shared Inst As globVars = Nothing                             'this is the self-setting key to individualize globVars
   Protected mIdentity As System.Security.Principal.WindowsIdentity        'this is the back-up identity determiner
#End Region

#Region "Private Functions"
   Private Sub New()
       mIdentity = System.Security.Principal.WindowsIdentity.GetCurrent    'on every new instance, reset the identity
   End Sub
#End Region
#Region "Read Only Properties"

   Public ReadOnly Property GetIdentity()
       Get
           Return mIdentity
       End Get
   End Property
#End Region
#Region "Public Functions"
   Public Shared Function GetInstance() As globVars
       If Inst Is Nothing Then
           Inst = New globVars
       End If
       Return Inst
   End Function
   Public Shared Sub Setup()
       Inst = New globVars
   End Sub

#End Region

 

In your global.asax, in the StartSession, invoke the class like this:

 

Dim glob as globVars
glob = globVars.getinstance
glob.Setup

 

Now set every variable you need to pass as a property in the new public property

 

  Private mUser As String

  Public Property sUser() As String
       Get
           Return mUser
       End Get
       Set(ByVal value As String)
           mUser = value
       End Set
   End Property

 

You can now set a value for sUser in one page and retrieve it in the next

 

The class DOES tend to persist when you kill the site, because SessionEnd and ApplicationEnd don't always work in .Net. Therefore you re-invoke it with every session

 

Other sessions will have no affect on your class, however, as is it is invoked against the windows identity

[PlausiblyDamp]

If you cannot rely on the page being posted back then your solution is probably the best. If someone is using some form of pop-up / cookie blocker then there is nothing you can do except 'educate' them to either allow cookies from your app or just live with the problem.

[Gill Bates]

You can also perform an XmlHttp request in the background and post the form elements back to the server.