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'KEEPING THE VIEWSTATE OUT OF THE ASPX PAGE
'Autor.: R�gis Daniel de Oliveira
'E-Mail: regisxp@hotmail.com
'Date..: 07/2005
'Main Reserach Source:
'http://www.eggheadcafe.com/articles/20040613.asp
Imports System.Configuration.ConfigurationSettings
Imports System.Diagnostics
Public Class VSPage
Inherits System.Web.UI.Page
Protected Overrides Sub SavePageStateToPersistenceMedium(ByVal viewState As Object)
Dim VSKey As String 'String that will hold the Unique Key used to reference this ViewState data
Debug.WriteLine(MyBase.Session.SessionID)
'Create the key based on the SessionID, on the Request.RawUrl
'and on the Ticks representated by the exact time while the page is being saved
VSKey = "VIEWSTATE_" & MyBase.Session.SessionID & "_" & Request.RawUrl & "_" & Date.Now.Ticks.ToString
'Check if the ServerSideViewState is Activated
If UCase(AppSettings("ServerSideViewState")) = "TRUE" Then
'Check were we will save the ViewState Data
If UCase(AppSettings("ViewStateStore")) = "CACHE" Then
'Store the ViewState on Cache
Cache.Add(VSKey, viewState, Nothing, Date.Now.AddMinutes(Session.Timeout), _
Cache.NoSlidingExpiration, Web.Caching.CacheItemPriority.Default, Nothing)
'The ViewStateData will be Saved on the SESSION
Else
Dim VsDataTable As DataTable
Dim DbRow As DataRow
'Check if the ViewState DataTable are on the Session
If IsNothing(Session("__VSDataTable")) Then
'No, it's not. Create it...
Dim PkColumn(1), DbColumn As DataColumn
VsDataTable = New DataTable("VState") 'Create the DataTable
'Column 1 - Name: VSKey - PrimaryKey
DbColumn = New DataColumn("VSKey", GetType(String))
VsDataTable.Columns.Add(DbColumn)
PkColumn(0) = DbColumn
VsDataTable.PrimaryKey = PkColumn
'Column 2 - Name: ViewStateData
DbColumn = New DataColumn("VSData", GetType(Object))
VsDataTable.Columns.Add(DbColumn)
'Column 3 - Name: DateTime
DbColumn = New DataColumn("DateTime", GetType(Date))
VsDataTable.Columns.Add(DbColumn)
Else
'The ViewState DataTable is already on the UserSession
VsDataTable = Session("__VSDataTable")
End If
'Check if we already have a ViewState saved with the same key.
'If yes, update it instead of creating a new row. (This is very dificult to happen)
DbRow = VsDataTable.Rows.Find(VSKey)
If Not IsNothing(DbRow) Then
'Row found!!! Update instead of creating a new one...
DbRow("VsData") = viewState
Else
'Create a new row...
DbRow = VsDataTable.NewRow
DbRow("VSKey") = VSKey
DbRow("VsData") = viewState
DbRow("DateTime") = Date.Now
VsDataTable.Rows.Add(DbRow)
End If
'Check if our DataTable is OverSized...
If Convert.ToInt16(AppSettings("ViewStateTableSize")) < VsDataTable.Rows.Count Then
Debug.WriteLine("Deleting ViewState Created On " & DbRow(2) & ",ID " & DbRow(0))
VsDataTable.Rows(0).Delete() 'Delete the 1st line.
End If
'Store the DataTable on the Session.
Session("__VSDataTable") = VsDataTable
End If
'Register a HiddenField on the Page, that contains ONLY the UniqueKey generated.
'With this, we'll be able to find with ViewState is from this page, by retrieving these value.
RegisterHiddenField("__VIEWSTATE_KEY", VSKey)
Else
'Call the normal process.
MyBase.SavePageStateToPersistenceMedium(viewState)
End If
End Sub
Protected Overrides Function LoadPageStateFromPersistenceMedium() As Object
'Verifica se o ServerSideViewState est� ativado
If UCase(AppSettings("ServerSideViewState")) = "TRUE" Then
Dim VSKey As String 'ViewState UniqueKey
VSKey = Request.Form("__VIEWSTATE_KEY") 'Request the Key from the page and validade it.
If Not VSKey.StartsWith("VIEWSTATE_") Then
Throw New Exception("Invalid VIEWSTATE Key: " & VSKey)
End If
'Verify which modality was used to save ViewState
If UCase(AppSettings("ViewStateStore")) = "CACHE" Then
Return Cache(VSKey)
Else
Dim VsDataTable As DataTable
Dim DbRow As DataRow
VsDataTable = Session("__VSDataTable")
DbRow = VsDataTable.Rows.Find(VSKey)
If IsNothing(DbRow) Then
Throw New Exception("VIEWStateKey not Found. Consider increasing the ViewStateTableSize parameter on Web.Config file.")
End If
Return DbRow("VsData")
End If
Else
'Return the ViewState using the Norma Method
Return MyBase.LoadPageStateFromPersistenceMedium()
End If
End Function
End Class
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Régis Daniel is currently living in Itaúna, MG, Brazil. He works with programming since 1999 and actualy works as IT Manager on a wholesaler company. He has experiency as Oracle DBA, and also worked as a PalmOS developer using CodeWarrior with C/C++.
Now a days he works on .NET Framework, developing solutions on Visual Basic.NET and ASP.NET. During his spare time, he likes reading books, watching movies and pratices some outdoor activities, like Trekking and Camping.