How to Persist Variable on Postback

Question

I created a single page (with code behind .vb) and created Public intFileID As Integer

in the Page load I check for the querystring and assign it if available or set intFileID = 0.

Public intFileID As Integer = 0  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load     If Not Page.IsPostBack Then         If Not Request.QueryString("fileid") Is Nothing Then             intFileID = CInt(Request.QueryString("fileid"))         End If          If intFileID > 0 Then             GetFile(intFileID)         End If     End If End Sub  Private Sub GetFile()     'uses intFileID to retrieve the specific record from database and set's the various textbox.text End Sub 

There is a click event for the Submit button that inserts or updates a record based on the value of the intFileID variable. I need to be able to persist that value on postback for it all to work.

The page simply inserts or updates a record in a SQL database. I'm not using a gridview,formview,detailsview, or any other rad type object which persists the key value by itself and I don't want to use any of them.

How can I persist the value set in intFileID without creating something in the HTML which could possibly be changed.

[EDIT] Changed Page_Load to use ViewState to persist the intFileID value

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load     If Not Page.IsPostBack Then         If Not Request.QueryString("fileid") Is Nothing Then             intFileID = CInt(Request.QueryString("fileid"))         End If          If intFileID > 0 Then             GetFile(intFileID)         End If          ViewState("intFileID") = intFileID     Else         intFileID = ViewState("intFileID")     End If End Sub 

Answer 1

As others have pointed out, you can store it in the Session or the ViewState. If it's page specific, I like to store it in the ViewState as opposed to the Session, but I don't know if one method is generally preferred over the other.

In VB, you would store an item in the ViewState like:

ViewState(key) = value 

And retrieve it like:

value = ViewState(key)