On Postback placeholder controls disappearing

Question

Within my webpage I am loading usercontrols within a placeholder. Each of these user controls triggers a postback when an ajaxcontroltoolkit rating is changed. The problem I am having is that if I use

If (Not IsPostBack is Nothing)

the controls within the placeholder disappear on post.

My Page_Load looks like this currently

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Session("ProId") = Nothing
    Session("FolId") = Nothing
    Dim ProId As Integer
    If (Not Request.QueryString("ProjectID") Is Nothing) Then
        ProId = Convert.ToInt32(Request.QueryString("ProjectID").ToString())
        Session("ProId") = Request.QueryString("ProjectID").ToString()
    End If
    Dim FolId As Integer
    If (Not Request.QueryString("FolderID") Is Nothing) Then
        FolId = Convert.ToInt32(Request.QueryString("FolderID").ToString())
        Session("FolId") = Request.QueryString("FolderID").ToString()
    End If
    objUser = New BSSiteUser(CInt(Page.User.SiteUser.intID))
    objProject = New BSProject(ProId)
    objFolder = New BSFolder(objUser.SiteUserID, FolId)
    objOrganization = New BSOrganization(objProject.intOrganizationID, objUser.SiteUserID)
    Me.Load_SubcontractorList()
    Me.Load_EvaluationList(1)
    Me.Load_EvaluationList(2)
    Me.lblorganization.Text = objOrganization.CompanyName
    Me.lblprojectname.Text = objProject.strProjectName
    Me.lblprojectnumber.Text = objProject.strProjectNumber
    Me.lbldatecreated.Text = Date.Now.Date.ToString()
End Sub

The Load_EvaluationList is what loads the user controls, if I place the IsPostBack check around those two, the controls disappear, what could be the problem

Answer 1

I am abandoning this question as a decision was made to go a different route

Answer 2

Dynamically added controls disappear on postback as you are working with a brand new instance of your page. In order for you to keep them you are going to have to recreate them for any postback that occurs.

It is also important to note that if you want your ViewState to be retained you should create your user controls on Page Init and not Page Load as loading of ViewState data back to the controls happens before the Load event.

Answer 3

If you are dynamically adding controls then on every postback you have to add control again.

try using if(Not IsPostBack) or (IsPostBack) instead of comparing it with Nothing.

Here I am simply adding a textbox dynamically on postback and it will stay in every postback.

     Partial Class _Default
        Inherits System.Web.UI.Page

      Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If (IsPostBack) Then
        Dim t As TextBox = New TextBox()
        form1.Controls.Add(t)

    End If

End Sub

End Class

You can put the controls you are trying to add dynamically in one function/method/subroutine and just call inside of Load.

Update

If you want your data to stay in the controls you have to save the data in the viewstate. You will have to create control again no matter what but before control is sent back to user get their data from the view state. It is described with example here.

http://forums.asp.net/t/1186195.aspx/1