March 2nd, 2006

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Compressing ASP.NET 2.0 Viewstate

One thing I was looking forward with asp.net 2.0 release was improved viewstate optimization. The truth is it has improved, but for me there is still something desirable to be had.

Where I have run into the problems is a web application I am working on the must allow the user to add an infinate amount of web controls dynamically. The results below are pretty amazing. I ended up using SharpZipLib for the compressing algorithm.

Test Scenerio: One web page with that ended up with 116 asp.net web controls add to it.

Result of ViewState Size:
Before Compression: 43.3 KB
After Compression using SharpZipLib: 3.50 KB

Below is the code to get you started

Imports System.IO
Imports Zip = ICSharpCode.SharpZipLib.Zip.Compression
 
Public Class PageViewStateZip : Inherits System.Web.UI.Page
 
    Protected Overrides Function LoadPageStateFromPersistenceMedium() As Object
        Dim vState As String = Me.Request.Form(“__VSTATE”)
        Dim bytes As Byte() = System.Convert.FromBase64String(vState)
        bytes = vioZip.Decompress(bytes)
        Dim format As New LosFormatter
 
        Return format.Deserialize(System.Convert.ToBase64String(bytes))
 
    End Function
 
    Protected Overrides Sub SavePageStateToPersistenceMedium(ByVal viewState As Object)
        Dim format As New LosFormatter
        Dim writer As New StringWriter
        format.Serialize(writer, viewState)
        Dim viewStateStr As String = writer.ToString()
        Dim bytes As Byte() = System.Convert.FromBase64String(viewStateStr)
        bytes = vioZip.Compress(bytes)
        Dim vStateStr As String = System.Convert.ToBase64String(bytes)
        RegisterHiddenField(“__VSTATE”, vStateStr)
 
    End Sub
 
End Class
 
 
Public Class vioZip
    Shared Function Compress(ByVal bytes() As Byte) As Byte()
        Dim memory As New MemoryStream
        Dim stream = New Zip.Streams.DeflaterOutputStream(memory, _
New Zip.Deflater(Zip.Deflater.BEST_COMPRESSION), 131072)
        stream.Write(bytes, 0, bytes.Length)
        stream.Close()
        Return memory.ToArray()
    End Function
 
    Shared Function Decompress(ByVal bytes() As Byte) As Byte()
        Dim stream = New Zip.Streams.InflaterInputStream(New MemoryStream(bytes))
        Dim memory As New MemoryStream
        Dim writeData(4096) As Byte
        Dim size As Integer
        While True
            size = stream.Read(writeData, 0, writeData.Length)
 
            If size > 0 Then memory.Write(writeData, 0, size) Else Exit While
        End While
        stream.Close()
        Return memory.ToArray()
    End Function
 
End Class

Written by Tim on March 2nd, 2006 with 27 comments.
Read more articles on asp.net.

Dynamic Placeholder that Saves Child Controls View State

One asp.net custom control that I am loving right now is Denis Baur’s Dynamic PlaceHolder. I’m having to do an web application that must allow for an infinite number of standard web controls and maintain state as these are entered. I went down the AJAX.NET Professional route for a minute but ran into some issues. Instead of recreating the controls on Page_INIT on every request to add a control, I’m able to add to the the new controls to the placeholder list.
Example:
Function AddProduct(Byval strPN as String)


Dim Count As Int32 = CType(ViewState(strPN & "Count_v"), Int32)

Count += 1 'increase viewstate count
Dim ddlProduct as New DropDownList

with ddlproduct

.id = "ddl" & strPN "Product" & Count.ToString()

dphP.Controls.Add(ddlproduct) 'add to dynamic placeholder

end with
ViewState(pn & "Count_v") = Count 'add back to viewstate count

End Function

Written by Tim on March 2nd, 2006 with 4 comments.
Read more articles on asp.net.