ASP.NET Viewstate bug?

[michela rossi]

Hi,

Don't know if anyone can help:

We have a web control that shows a collection as a series of
checkboxes. Preselected items are passed in and the user is free to
change the checked items. This is then read out of a property and
saved in the database.

However there is a problem persisting the state of the control between
postbacks. The user-selected items are stored in a class that
derives from arraylist, called UpdateAwareArra yList, which is just
aware of any changes made to it.
I'm storing this class in viewstate with the following code (in
VB.net)
Protected Overrides Function SaveViewState() As Object
Dim baseState As Object = MyBase.SaveView State()
Dim CombinedStates( 1) As Object
CombinedStates( 0) = baseState
CombinedStates( 1) = CType(arSelecte dItems, UpdateAwareArra yList)
Return CombinedStates
End Function
The class is declared as (in C#):

[Serializable()]
public class UpdateAwareArra yList : ArrayList, ISerializable

That seems to work, however when I try and get the class out of
viewstate, whats returned is a class of type ArrayList, not
UpdateAwareArra yList. I don't know why. As an attempt to work around
this I created a temporary arraylist to take the viewstate read, and
added its members to a variable of the right class:
Protected Overrides Sub LoadViewState(B yVal savedState As Object)

If Not (savedState Is Nothing) Then

Dim myState As Object() = CType(savedStat e, Object())
If Not (myState(0) Is Nothing) Then
MyBase.LoadView State(myState(0 ))
End If

Dim arTemp As ArrayList
If Not (myState(1) Is Nothing) Then arTemp = myState(1)
If arTemp.Count > 0 Then
arSelectedItems = New UpdateAwareArra yList()
Dim intTempCounter As Int32
For intTempCounter = 0 To arTemp.Count - 1
arSelectedItems .Add(arTemp(int TempCounter))
Next
End If

End If
End Sub
This works for the first postback, however on the second I get a
corrupt viewstate error on the page.

[Cor]

Hi Michela,
May I ask where you store the data when you do the postback?
Cor

[michela rossi]

"Cor" <no*@non.com> wrote in message news:<3f******* *************** *@reader20.wxs. nl>...

Hi Michela,
May I ask where you store the data when you do the postback?
Cor

I'm trying to store the data in the viewstate on the browser - the form is
posting back because of other controls: eg a checkbox control with
auto-postback set to true. When this posts back when the checkbox is
clicked, the control with the problem needs to store its state in viewstate,
otherwise the state is lost.

[Cor]

Hi Michela,
Did you read this in the documentation.
Note The data must be in a format compatible with view state. For example,
to store a dataset in view state, you should first convert it to a string
representation.
I did not see any conversion in your code to string (there are examples
given in the documentation with streamreader and stringreader.)
(The only format I could find when I was reading this fast usable to
viewstate (I don't know if there are more, but it can be the problem).
Succes
Cor

[michela rossi]

The UpdateAwareArra yList class implements Iserializable, and has the
following 2 methods

public UpdateAwareArra yList(Serializa tionInfo info,
StreamingContex t context)

{

int intItemCount = (Int32)
info.GetValue(" intItemCount", typeof(Int32));

for (int intItemCounter = 0 ; intItemCounter <
intItemCount; intItemCounter+ +)

{

this.Add(info.G etValue("Item" +
intItemCounter, typeof(Object)) );

}

blnStartMonitor ing = (bool)
info.GetValue(" blnStartMonitor ing", blnStartMonitor ing.GetType());

blnChanged = (bool) info.GetValue(" blnChanged",
blnChanged.GetT ype());

}

public void GetObjectData(S erializationInf o info,
StreamingContex t context)

{

info.AddValue(" intItemCount", this.Count);

for (int intItemCounter = 0; intItemCounter <
this.Count; intItemCounter+ +)

{

info.AddValue(" Item" +
intItemCounter. ToString(), this[intItemCounter]);

}

info.AddValue(" blnStartMonitor ing",
blnStartMonitor ing);

info.AddValue(" blnChanged", blnChanged);

}

This *should* store the state automatically when the class is added to
the viewstate, or so I had hoped.

[Cor]

Michela,
Did you look here
http://msdn.microsoft.com/library/de...teproperty.asp
It is so nice decribed that I think you can do it yourself.
If problems I will try to help you further OK?
Cor