Store with viewstate problem

[songjuju]

Dear all:

I tried to use the viewstate in store event "OnBeforeStoreChanged" like the code below.

In .Aspx

<ext:Store ID="Store1" runat="server" OnBeforeStoreChanged="Store1_BeforeChange">

In .Aspx.cs

protected void Store1_BeforeChange(object sender, BeforeStoreChangedEventArgs e)
{
            ViewState["GridList"] = e.DataHandler.XmlData;
            .....
}

The ViewState["GridList"] should save the xml data after the Store saving, but it doesn't.