Compressing viewstate is adding another hidden field with same id as __VIEWSTATE - asp.net

Question

I am trying to compress viewstate in ASP.Net 4.0, so the page loads more quickly for heavily bloated viewstate pages.
However, when I view source of page in browser, I am finding 2 hidden fields with same name and id of '__VIEWSTATE'.
My code is as below. How can I compress the view state but let it be stored in its original hidden field without creating another duplicate hidden field?
protected override void SavePageStateToPersistenceMedium(object viewState)
{
byte[] viewStateArray;
using (MemoryStream memoryStream = new MemoryStream())
{
_objectStateFormatter.Serialize(memoryStream, viewState);
viewStateArray = memoryStream.ToArray();
}
ClientScript.RegisterHiddenField("__VIEWSTATE",
Convert.ToBase64String(GZip.Compress(viewStateArray)));
}

Answer 1

using System.IO;
using System.IO.Compression;
using System.Web.UI;
public class PageCompressed : System.Web.UI.Page
{
private ObjectStateFormatter _formatter = new ObjectStateFormatter();
protected override void SavePageStateToPersistenceMedium(object viewState)
{
MemoryStream ms = new MemoryStream();
_formatter.Serialize(ms, viewState);
byte[] viewStateArray = ms.ToArray();
ClientScript.RegisterHiddenField("__CVIEWSTATE", Convert.ToBase64String(_Compress(viewStateArray)));
}
protected override object LoadPageStateFromPersistenceMedium()
{
string vsString = Request.Form["__CVIEWSTATE"];
byte[] bytes = Convert.FromBase64String(vsString);
bytes = _DeCompress(bytes);
return _formatter.Deserialize(Convert.ToBase64String(bytes));
}
private byte[] _Compress(byte[] inputBytes)
{
MemoryStream m = new MemoryStream();
GZipStream zip = new GZipStream(m, CompressionMode.Compress, true);
zip.Write(inputBytes, 0, inputBytes.Length);
zip.Close();
return m.ToArray();
}
private byte[] _DeCompress(byte[] inputBytes)
{
MemoryStream m = new MemoryStream(inputBytes);
MemoryStream mout = new MemoryStream();
GZipStream zip = new GZipStream(m, CompressionMode.Decompress, true);
do
{
byte[] bBuffer = new byte[4097];
int iRead = zip.Read(bBuffer, 0, bBuffer.Length);
if (iRead > 0)
{
mout.Write(bBuffer, 0, iRead);
}
else
{
break;
}
} while (true);
zip.Close();
return mout.ToArray();
}
}
you can use this Interface Class to compress viewstate by inheriting from it like this in code behind for every page
public partial class Default : PageCompressed