Byte loss with response filter

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VB9

VB

ASP.NET

Hi,

the last day, I decided to improve the performance of my website, so I decided to compress the responses.

I've created a module that I've registered in the Web.config. This module registers an handler for the PostRequestHandlerExecute event. Here the module sets a System.IO.Compression.GZipStream as the filter of the response. The problem comes when the response MIME type is text/html because I want to minify html code. I wrote a new stream to do that and it works fine, but when I combine it with the GZipStream, there is a loss of data.

Example: at the end of the HTML code i find "</htm" instead of "</html>"

My idea was creating a sort of "stream chain": a MinifyHTMLStream that minifies html code before writing data in a GZipStream that compresses minified html code before sending it to the client.

So, the question is: why the response filter works fine only when in the "stream chain" there is only 1 stream?

Here is the code:

'filter to register
            Dim NewFilter As IO.Stream = App.Response.Filter

            'finds the accept-encoding
            Dim strAcceptEncoding As String = App.Request.Headers("Accept-Encoding")

            'checks if the client accepts encoding
            If Not String.IsNullOrEmpty(strAcceptEncoding) Then

                'if the clients supports gzip
                If strAcceptEncoding.ToLower.Contains("gzip") OrElse strAcceptEncoding = "*" Then
                    'sets the filter
                    NewFilter = New IO.Compression.GZipStream(NewFilter, IO.Compression.CompressionMode.Compress)
                    'sets the header for the client
                    App.Response.AppendHeader("Content-Encoding", "gzip")
                ElseIf strAcceptEncoding.ToLower.Contains("deflate") Then
                    'sets the filter
                    NewFilter = New IO.Compression.DeflateStream(NewFilter, IO.Compression.CompressionMode.Compress)
                    'sets the header for the client
                    App.Response.AppendHeader("Content-Encoding", "deflate")
                End If
            End If

            'if the response type is html
            If App.Response.ContentType.ToLower = "text/html" Then
                '--------------------------------------------
                'HERE IS MY STREAM FOR HTML CODE MINIFYING
                'NewFilter = New MinifyHTMLStream(NewFilter)
                '--------------------------------------------

            End If

            'sets the filter
            App.Response.Filter = NewFilter

Thanks for your help!