ASP.NET: Compress ViewState

Question

What are the latest and greatest ways to compress the ASP.NET ViewState content?

What about the performance of this? Is it worth it to keep the pages quick and minimize data-traffic?

How can I make:

<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" 
value="/wEPDwUKMTM4Mjc3NDEyOWQYAQUeX19Db250cm9sc1JlcXVpcmVQb3N0QmFja0tleV9fFgkFLGN0b
DAwJENvbnRlbnRQbGFjZUhvbGRlcl9NYWluQ29udGVudCRSYWRCdXQxBSxjdGwwMCRDb250ZW50UGxhY2VIb
2xkZXJfTWFpbkNvbnRlbnQkUmFkQnV0MQUsY3RsMDAkQ29udGVudFBsYWNlSG9sZGVyX01haW5Db250ZW50J
FJhZEJ1dDIFLGN0bDAwJENvbnRlbnRQbGFjZUhvbGRlcl9NYWluQ29udGVudCRSYWRCdXQyBSxjdGwwMCRDb
250ZW50UGxhY2VIb2xkZXJfTWFpbkNvbnRlbnQkUmFkQnV0MwUsY3RsMDAkQ29udGVudFBsYWNlSG9sZGVyX
01haW5Db250ZW50JFJhZEJ1dDQFLGN0bDAwJENvbnRlbnRQbGFjZUhvbGRlcl9NYWluQ29udGVudCRSYWRCd
XQ0BSxjdGwwMCRDb250ZW50UGxhY2VIb2xkZXJfTWFpbkNvbnRlbnQkUmFkQnV0NQUsY3RsMDAkQ29udGVud
FBsYWNlSG9sZGVyX01haW5Db250ZW50JFJhZEJ1dDXz21BS0eJ7991pzjjj4VXbs2fGBw==" />

Into sometning like this:

<input type="hidden" name="__VIEWSTATE"  id="__VIEWSTATE" 
value="/wEPDwUKMTM4Mjc3N==" />

Answer 1

Again, after some research into this I summarized my findings in a blog-post about Compressing View State.

To save a compressed View State, this is what I did:

protected override void SavePageStateToPersistenceMedium(object state) {
    SaveCompressedPageState(state);
}

private void SaveCompressedPageState(object state) {
    byte[] viewStateBytes;
    using(MemoryStream stream = new MemoryStream()) {
        ObjectStateFormatter formatter = new ObjectStateFormatter();
        formatter.Serialize(stream, state);
        viewStateBytes = stream.ToArray();
    }

    byte[] compressed = CompressionHelper.Compress(viewStateBytes);
    string compressedBase64 = Convert.ToBase64String(compressed);

    ClientScript.RegisterHiddenField(ViewStateFieldName, compressedBase64);
}

And for the loading-part, this code made it work for me:

protected override object LoadPageStateFromPersistenceMedium() {
    return LoadCompressedPageState();
}

private object LoadCompressedPageState() {
    string viewState = Request.Form[ViewStateFieldName];
    if(string.IsNullOrEmpty(viewState)) {
        return string.Empty;
    }

    byte[] decompressed = CompressionHelper.Decompress(viewState);
    string decompressedBase64 = Convert.ToBase64String(decompressed);

    ObjectStateFormatter formatter = new ObjectStateFormatter();
    return formatter.Deserialize(decompressedBase64);
}

Answer 2

Compressing view state fails in certain cases: - If you are using update panel on page don’t use compression mode. - If somehow you are changing the view state in result of ICallBack code don’t use compression mode, as this will don’t reflect the correct view state on post back.

Answer 3

1. Avoid using ViewState
2. Use compression on the IIS server.
3. You can wireup something that will compress the viewstate into and out of a page by doing something like:

public abstract class PageBase : System.Web.UI.Page
{
    private ObjectStateFormatter _formatter = new ObjectStateFormatter();

    private static byte[] Compress( byte[] data )
    {
            var compressedData = new MemoryStream();
            var compressStream = new GZipStream(output, CompressionMode.Compress, true);
            compressStream.Write(data, 0, data.Length);
            compressStream.Close();
            return compressedData.ToArray();
    }
    private static byte[] Uncompress( byte[] data )
    {
            var compressedData = new MemoryStream();
            input.Write(compressedData, 0, compressedData.Length);
            input.Position = 0;
            var compressStream = new GZipStream(compressedData, CompressionMode.Decompress, true);
            var uncompressedData = new MemoryStream();
            var buffer = new byte[64];
            var read = compressStream.Read(buffer, 0, buffer.Length);

            while (read > 0)
            {
                uncompressedData.Write(buffer, 0, read);
                read = compressStream.Read(buffer, 0, buffer.Length);
            }
            compressStream.Close();
            return uncompressedData.ToArray();
    }
    protected override void SavePageStateToPersistenceMedium(object viewState)
    {
        var ms = new MemoryStream();
        _formatter.Serialize(ms, viewState);
        var viewStateBytes = ms.ToArray();
        ClientScript.RegisterHiddenField("__COMPRESSED_VIEWSTATE"
            , Convert.ToBase64String( Compress(viewStateArray)) );
    }
    protected override object LoadPageStateFromPersistenceMedium()
    {
        var compressedViewState = Request.Form["__COMPRESSED_VIEWSTATE"];
        var bytes = Uncompress( Convert.FromBase64String( compressedViewState ) );
        return _formatter.Deserialize( Convert.ToBase64String( bytes ) );
    }
}