HttpContext.Current.Response.Filter: Response filter is not valid

Question

Busy with some legacy code to write to csv/xls:

// Set up response
string filename = "ErrorControlExport";
string attachment = "attachment; filename=" + filename + "_" + DateTime.UtcNow.ToFileTime() + "." + extension;
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ClearHeaders();
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.AddHeader("content-disposition", attachment);
HttpContext.Current.Response.ContentType = contentType;
HttpContext.Current.Response.AddHeader("Pragma", "public");
// Clear any settings (such as GZip)
HttpContext.Current.Response.Filter = null;//exception occurs here

// Add BOM to force recognition of UTF-8
byte[] bom = new byte[] { 0xef, 0xbb, 0xbf };
HttpContext.Current.Response.BinaryWrite(bom);

However when the code reaches:

// Clear any settings (such as GZip)
HttpContext.Current.Response.Filter = null;//exception occurs here

it throws a HttpException of

Response filter is not valid.

So my questions are:

1) How do I set the filter to an empty or default filter?

2) Is it even necessary?

Thanks in advance for your help

Answer 1

check this post. Even though it talks about ASp.Net 3.5, I tried it and it works. I just read the filter var filter = Response.Filter and then assigned null to it Response.Filter = null

Answer 2

Besides @Nileshs' comment/answer (+1 to it as I used this method)

Another option is to create an Empty filter:

/// <summary>
/// Creates and empty filter for HttpResponse.Filter (i.e no proessing is done on the text before writting to the stream)
/// </summary>
class EmptyFilter : MemoryStream
{
    private string source = string.Empty;
    private readonly Stream filter;


    public EmptyFilter(HttpResponse httpResponseBase)
    {
        this.filter = httpResponseBase.Filter;
    }


    public override void Write(byte[] buffer, int offset, int count)
    {
        this.source = Encoding.UTF8.GetString(buffer);

        this.filter.Write(Encoding.UTF8.GetBytes(this.source), offset, Encoding.UTF8.GetByteCount(this.source));
    }
}

than simply set to:

HttpContext.Current.Response.Filter = new EmptyFilter(HttpContext.Current.Response);