Hi Ana,
Please post the simplified relevant code sections so that we can try out
with that code.

I found some solutions in different scenarios

 "Disable the viewstate for the controls if not required"
http://www.believetech.com/wordpress_blog/?p=106

Don't use "Cancel" as a CommandName in the ItemTemplate
http://www.dotnetgoodies.com/article/ASP.NET_Web_Application_Development/56/Failed_to_load_viewstate_The_control_tree_into_which_viewstate_is_being_loaded_must_match_the_control_tree_that_was_used_to_save_viewstate_during_the_.aspx

"Clear the ViewState in the base.OnInit() if Request isn't a PostBack"
http://www.developmentnow.com/g/15_2006_4_0_0_746505/Failed-to-load-viewstate.htm

Regards,
Raghu

On Tue, Sep 15, 2009 at 12:26 AM, Ana <[email protected]> wrote:

>
> Just an update to the problem:
>
> I’m showing/hiding controls dynamically not in the FormView, but in
> the GridView associated to the FormView. For instance, I have a
> MoveButton to move field and some fields can only be moved if they
> have certain values (for example if field = true). Because the
> GridView is allowing paging, what happens is that row n in page 1 may
> have MoveButton.Visible = False, but the same row in page 2 may have
> MoveButton.Visible = True.
> Besides, I'm sorting the Gridview according to 2 criteria. When
> sorting according to one of these criteria, I'm hiding a column in the
> GridView. So the solution is not as simple as only enable/disable
> controls.
>
> Any suggestions?
>
> Thanks,
>
> Ana
>
>
> On Sep 14, 12:41 pm, Processor Devil <[email protected]>
> wrote:
> > Well, it looks like that is the problem...Try not to hide it, but to
> disable
> > it :)
> >
> > 2009/9/14 Ana <[email protected]>
>  >
> >
> >
> > > I came back to the page I was working before to see if I find what is
> > > firing this error message. I just realized that, even though I'm not
> > > creating controls dynamically, I'm showing/hiding controls dynamically
> > > in the FormView. For instance, some fields can only be updated if the
> > > user is the administrator; when the user is not the administrator,
> > > what I'm doing is hide the control (usually a TextBox). Can this be
> > > the reason why I'm having the error message?
> >
> > > Thanks,
> >
> > > Ana
> >
> > > On Sep 14, 9:48 am, Ana <[email protected]> wrote:
> > > > Hi,
> >
> > > > Apparently what was happening was that in the EditItemTemplate the
> > > > formView had a Label, but in the InsertItemTemplate and ItemTemplate
> > > > this Label was not there. I removed the Label from the
> > > > EditItemTemplate and the error message is not being fired anymore.
> Can
> > > > anyone give me more details about this?
> >
> > > > Thanks,
> >
> > > > Ana
> >
> > > > On Sep 14, 9:32 am, Ana <[email protected]> wrote:
> >
> > > > > This problem is really driving me nuts! I'm working in a diferent
> page
> > > > > now, and am having the same problem (always associated with a
> > > > > formview). In the page I'm working now, the problem happened when I
> > > > > updated a record. I updated a record in the FormView, the GridView
> was
> > > > > bound correctly, but when I tried to update another record the
> "fail
> > > > > to load view state" error was fired again.
> > > > > I'm not creating any controls dinamically. I can't understand what
> is
> > > > > happening at all!
> > > > > I don't think that make EnableEventValidation="false" is the better
> > > > > way to solve this problem. As you said, Raghupathi, "we are giving
> a
> > > > > way to hacker to intrude by disabling the event validation".
> > > > > Anyone here already had this problem and can help me with this? I
> > > > > appreciate all help!
> >
> > > > > Thanks,
> >
> > > > > Ana
> >
> > > > > On Sep 9, 11:55 pm, Raghupathi Kamuni <[email protected]>
> wrote:
> >
> > > > > > To solve this problem,
> >
> > > > > > <pages enableEventValidation="false"/> in Web.Config or,
> > > > > > <%@ Page EnableEventValidation="false" %> in a page attribute
> >
> > > > > > By doing this, we are giving a way to hacker to intrude by
> disabling
> > > the
> > > > > > event validation.
> >
> > > > > > This can be prevented by use of RegisterForEventValidation
> methods of
> > > > > > ClientScriptManager class
> >
> > > > > > We need to register the server control ID with the all the
> possible
> > > values
> > > > > > that can be posted by JavaScript by that control in Render Event
> of
> > > the page
> > > > > > using
> >
> > > > > > ClientScript.RegisterForEventValidation()
> >
> > > > > > Check out this for the relavant articlehttp://
> > >www.codedigest.com/Articles/ASPNET/221_Using_JavaScript_Effect...
> >
> > > > > > On Wed, Sep 9, 2009 at 11:24 PM, Raghupathi Kamuni <
> > > [email protected]>wrote:
> >
> > > > > > > ViewState  and Dynamic Control
> > > > > > >
> http://geekswithblogs.net/FrostRed/archive/2007/02/17/106547.aspx
> >
> > >http://weblogs.asp.net/alessandro/archive/2008/01/04/failed-to-load-v.
> ..
> >
> > > > > > > On Wed, Sep 9, 2009 at 11:01 PM, Ana <
> [email protected]>
> > > wrote:
> >
> > > > > > >> Hi,
> >
> > > > > > >> In my page I have a Gridview and a FormView. For each row in
> the
> > > > > > >> GridView, there's a linkButton *Details* that shows the
> FormView
> > > with
> > > > > > >> the information about the selected record in the GridView.
> > > > > > >> In the FormView, users are able to edit and delete records.
> > > However,
> > > > > > >> every time I cancel the editing of a record and try to see the
> > > > > > >> formview for this record (clicking in *Details* on the
> GridView),
> > > I
> > > > > > >> have the following error message:
> >
> > > > > > >> --
> > > > > > >> Failed to load viewstate.  The control tree into which
> viewstate
> > > is
> > > > > > >> being loaded must match the control tree that was used to save
> > > > > > >> viewstate during the previous request.  For example, when
> adding
> > > > > > >> controls dynamically, the controls added during a post-back
> must
> > > match
> > > > > > >> the type and position of the controls added during the initial
> > > > > > >> request.
> > > > > > >> --
> >
> > > > > > >> What is happening here? Why this error message in being fired?
> >
> > > > > > >> Thanks in advance,
> >
> > > > > > >> Ana
>

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