How to compress JavaScript and CSS using gzip compression in Asp .Net 3.5 web application?

Question

How to compress JavaScript and CSS using gzip compression in Asp .Net 3.5 web application? Gzip compression results error in CSS menu and validators scripts.

Answer 1

Download gzip compression sample code and add it to your Global.asax file.

Answer 2

add the below code to Global.asax and put it into your root directory.

    
    


void Application_PreRequestHandlerExecute(object sender, EventArgs e)
{
    HttpApplication app = sender as HttpApplication;
    string acceptEncoding = app.Request.Headers["Accept-Encoding"];
    Stream prevUncompressedStream = app.Response.Filter;

    if (!(app.Context.CurrentHandler is Page ||
        app.Context.CurrentHandler.GetType().Name == "SyncSessionlessHandler") ||
        app.Request["HTTP_X_MICROSOFTAJAX"] != null)
        return;

    if (acceptEncoding == null || acceptEncoding.Length == 0)
        return;

    acceptEncoding = acceptEncoding.ToLower();

    if (acceptEncoding.Contains("deflate") || acceptEncoding == "*")
    {
        // defalte
        app.Response.Filter = new DeflateStream(prevUncompressedStream,
            CompressionMode.Compress);
        app.Response.AppendHeader("Content-Encoding", "deflate");
    } else if (acceptEncoding.Contains("gzip"))
    {
        // gzip
        app.Response.Filter = new GZipStream(prevUncompressedStream,
            CompressionMode.Compress);
        app.Response.AppendHeader("Content-Encoding", "gzip");
    }
}
 

Answer 3

Why don't you use HttpCompression? That would enable you to compress all static content including javascript and CSS files.

HttpCompression IIS 6

HttpCompression IIS 7

Answer 4

(I've been using this technique for quite a while - hence the vb.net code!)

Although compression is not supported by IIS 6.0, most browsers support basic gzip compression and they notify the server of this ability by sending a header in each request. The following piece of code shows how to use the System.IO.Compression namespace to add a filter to the output stream that compresses the output whilst checking and setting the correct headers.

 context.Response.Clear()
 context.Response.Buffer = True

 context.Response.AddHeader("content-disposition", String.Format( "attachment;filename={0}", fileName))
 context.Response.ContentEncoding = Encoding.UTF8

 context.Response.Cache.SetCacheability(HttpCacheability.Private)

 'Compress the output as it may be very large
 'When flushing or closing+ending the stream, the compression filter does not have a chance to write the compression footer
 'Therefore, make sure the compression filter stream is closed before flushing
 AddCompression(context)

 context.Response.ContentType = "application/vnd.ms-excel" 'This example was an excel doc

 'Write to response
 context.Response.Write(your-data-here)

 'context.Response.Flush() 'Do not flush if using compression
 'context.Response.Close()
 context.Response.End()

The AddCompression method checks the appropriate headers and adds a compression filter stream to the output:

'Add compression to the response stream
Public Sub AddCompression(ByVal context As HttpContext)

    Dim acceptEncoding As String = context.Request.Headers("Accept-Encoding")
    If acceptEncoding Is Nothing OrElse acceptEncoding.Length = 0 Then Return

    'Convert to lower to check
    acceptEncoding = acceptEncoding.ToLower

    'Gzip or Compress compression
    'Compress compression is quicker and performs better compression so try that first
    If (acceptEncoding.Contains("deflate")) Then

        context.Response.Filter = New DeflateStream(context.Response.Filter, CompressionMode.Compress)
        context.Response.AppendHeader("Content-Encoding", "deflate")

    ElseIf acceptEncoding.Contains("gzip") Then

        context.Response.Filter = New GZipStream(context.Response.Filter, CompressionMode.Compress)
        context.Response.AppendHeader("Content-Encoding", "gzip")

    End If

End Sub