Dim value disappears vb.net

Question

I'm trying to store a value in code behind so I don't have to clog my page with HiddenFields, but the value 'disappears'

I'm assuming it has to do with either scope or byval vs byref, but I don't know how I need to do it for it to work.

What I've tried to do is creating a Dim under my Partial Class, setting the value in a gridview.RowCommand, and then trying to get the value at a later button.Click

Partial Class CustNSSF_MinSide
Inherits System.Web.UI.Page
Dim vr As New vrClass
Dim _ActNo As String

Sub GV_Relations_RowCommand(ByVal sender As Object, ByVal e As GridViewCommandEventArgs) Handles GV_Relations.RowCommand
  _ActNo = GV_Relations.DataKeys(index)("ActSeqNo")

 Protected Sub btn_lagre_Click(sender As Object, e As System.EventArgs) Handles btn_lagre.Click
            Dim test = _ActNo

Tim Schmelter · Accepted Answer · 2014-10-06T07:59:30.537

The value disappears because all variables (or controls) are disposed at the end of every page's life-cycle. GV_Relations_RowCommand is triggered only on RowCommand and btn_lagre_Click is a different action. You could store this value in a Session variable, ViewState or (as you've done) in a HiddenField. So when the user clicked on btn_lagre, the previous action that caused RowCommand was a different postback, therefore the variable is Nothing.

So one way (apart from your HiddenField aproach), using ViewState:

Private Property ActSeqNo As System.Int32
    Get
        If ViewState("ActSeqNo") Is Nothing Then
            ViewState("ActSeqNo") = System.Int32.MinValue
        End If
        Return DirectCast(ViewState("ActSeqNo"), System.Int32)
    End Get
    Set(value As System.Int32)
        ViewState("ActSeqNo") = value
    End Set
End Property

Then you can set it in this way:

Me.ActSeqNo = System.Int32.Parse(GV_Relations.DataKeys(index)("ActSeqNo")))

Nine Options for Managing Persistent User State in ASP.NET

My boss is not a fan of Session and I feel like HiddenField is probably easier than ViewState. But at least I know why it isn't working and that's really all I needed I guess. Saves me time in the future :) — thokin, Oct 06 '14 at 08:09

score 0 · Answer 2 · answered Oct 06 '14 at 07:52

The variable will be clear every Postback. You need to store it either in the Viewstate or in the Session. You could do this:

Property _ActNo As String 
    Get 
        Return ViewState("_ActNo")
    End Get 
    Set(ByVal value As String)
        ViewState("_ActNo") = value
    End Set 
End Property

Dim value disappears vb.net

2 Answers2