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 32 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 2 comments.
Read more articles on asp.net.