What are the possibly situations that .net Viewstate could stop working?

Question

Consider the following code:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
        If Page.IsPostBack Then
            If ViewState("test") IsNot Nothing Then
                Response.Write((ViewState("test").ToString))
            Else 
                Response.Write("Viewstate is empty.")
            End If
        Else
            ViewState("test") = "viewstate is working."
        End If
    End Sub

This code doesn't work on a particular page in my application. Viewstate is not turned off in the Page directive. I can't figure out what's going on. : \

Oh i just figured it out. See if you notice it.

.<

Answer 1

You can turn off viewstate from the config file too.

<configuration>
  <appSettings>
    <Pages EnableViewState="false" />
  </appSettings>
</configuration>

Answer 2

Could you post more code from the page?

How do you trigger the postback? a simple button?

Answer 3

Are you SURE that you make a postback?

Do it write "Viewstate is empty"? Or just nothing?

Answer 4

Figured it out, someone had changed the Page_Load event to handle Page.Init

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init

Answer 5

Since you didn't answer your own post...

I'd say you are checking IsPostBack and accessing ViewState at the wrong stages:

Handles Me.Init

That should be

Handles Me.Load

right?

---

For debugging such headaches in ASP.NET I'd also like to add that tracing can often helps a lot.

You can enable tracing by adding this to web.config:

<configuration>
  <system.web>
    <trace enabled="true" pageOutput="true" requestLimit="40" localOnly="false"/>
  </system.web>
</configuration>

This will append the stack trace and whatnot to the end of every page, so you can trace the execution and (hopefully) find out the problem.

Answer 6

In my case I was writing data to a ViewState on Page_Init. This data was displaying nice on Page_Load and Page_PreRender, but it was not being persisted to page at the end of life-cycle. After postback ViewState was empty.

So, make sure that you write to ViewState AFTER Page_Init.