AddHeader "Content-Length" does not work in IIS7
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From: Abe Simpson on 21 Jul 2010 13:37 Well, dear Microsoft, thank you very effing much. This time you really screwed the pooch. The following file download code has worked with all versions of IIS prior to 7: Response.ContentType = "text/plain" Response.AddHeader "Content-Disposition", "attachment;filename=""file.txt""" Response.AddHeader "Content-Length", "3100" Response.BinaryWrite FileBody But on IIS7, it does not. Via elimination, I found the culprit to be the line Response.AddHeader "Content-Length", "3100" Remove it, and it works fine again (although there is no file size information, of course.) You can also disable both Enable Buffering and Enable Chunked Encoding under ASP settings, and it will work again. Great, ain't it? What gives! How long is M$ going to test our patience with tricks like that????? -- Abe
From: Dan on 22 Jul 2010 04:07 "Abe Simpson" <abe(a)simpson.com> wrote in message news:ebrCktPKLHA.4936(a)TK2MSFTNGP05.phx.gbl... > Well, dear Microsoft, thank you very effing much. This time you really > screwed the pooch. The following file download code has worked with all > versions of IIS prior to 7: > > Response.ContentType = "text/plain" > Response.AddHeader "Content-Disposition", > "attachment;filename=""file.txt""" > Response.AddHeader "Content-Length", "3100" > Response.BinaryWrite FileBody > > > But on IIS7, it does not. Via elimination, I found the culprit to be the > line > > Response.AddHeader "Content-Length", "3100" > > Remove it, and it works fine again (although there is no file size > information, of course.) > > You can also disable both Enable Buffering and Enable Chunked Encoding > under ASP settings, and it will work again. Great, ain't it? What gives! > How long is M$ going to test our patience with tricks like that????? > http://greenbytes.de/tech/webdav/rfc2616.html#rfc.section.4.4 Note the 3rd bullet point - you cannot use Content-Length with Transfer-Encoding (which is used for chunked encoding). http://msdn.microsoft.com/en-us/library/aa347544(VS.90).aspx EnableChunkedEncoding is True by default in IIS7. I can see how this could be annoying - I have a few applications which set Content-Length too. With this having been changed from IIS 6 to IIS 7 Microsoft should have put in provision handling for applications setting Content-Length - either disable Chunked Encoding for that response, or remove the Content-Length header automatically. I've never used the Content-Length header with buffering enabled in IIS 6 or earlier - by having buffering enabled IIS will automatically add the correct Content-Length header. I've only ever use Content-Length with buffering disabled and flushing the buffer in a loop using BinaryWrite in small pieces, as it's not possible for IIS to determine the amount of data being sent in total in this situation. If you check the response with Fiddler2 with buffering enabled, is IIS adding an additional Content-Length header itself? -- Dan
From: Dan on 22 Jul 2010 04:26
"Dan" <news(a)worldofspack.com> wrote in message news:ORoR4TXKLHA.3732(a)TK2MSFTNGP02.phx.gbl... > > "Abe Simpson" <abe(a)simpson.com> wrote in message > news:ebrCktPKLHA.4936(a)TK2MSFTNGP05.phx.gbl... >> Well, dear Microsoft, thank you very effing much. This time you really >> screwed the pooch. The following file download code has worked with all >> versions of IIS prior to 7: >> >> Response.ContentType = "text/plain" >> Response.AddHeader "Content-Disposition", >> "attachment;filename=""file.txt""" >> Response.AddHeader "Content-Length", "3100" >> Response.BinaryWrite FileBody >> >> >> But on IIS7, it does not. Via elimination, I found the culprit to be the >> line >> >> Response.AddHeader "Content-Length", "3100" >> >> Remove it, and it works fine again (although there is no file size >> information, of course.) >> >> You can also disable both Enable Buffering and Enable Chunked Encoding >> under ASP settings, and it will work again. Great, ain't it? What gives! >> How long is M$ going to test our patience with tricks like that????? >> > > http://greenbytes.de/tech/webdav/rfc2616.html#rfc.section.4.4 > > Note the 3rd bullet point - you cannot use Content-Length with > Transfer-Encoding (which is used for chunked encoding). > > http://msdn.microsoft.com/en-us/library/aa347544(VS.90).aspx > > EnableChunkedEncoding is True by default in IIS7. > > I can see how this could be annoying - I have a few applications which set > Content-Length too. With this having been changed from IIS 6 to IIS 7 > Microsoft should have put in provision handling for applications setting > Content-Length - either disable Chunked Encoding for that response, or > remove the Content-Length header automatically. > > I've never used the Content-Length header with buffering enabled in IIS 6 > or earlier - by having buffering enabled IIS will automatically add the > correct Content-Length header. I've only ever use Content-Length with > buffering disabled and flushing the buffer in a loop using BinaryWrite in > small pieces, as it's not possible for IIS to determine the amount of data > being sent in total in this situation. > > If you check the response with Fiddler2 with buffering enabled, is IIS > adding an additional Content-Length header itself? > Odd, according to the following article this should potentially affect IIS6 too as it's enabled by default http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/c9b722e8-189f-4bfe-8716-70bf8d2271df.mspx?mfr=true However, it will only be enabled for sites that are not using buffering - and as that is set on by default too. I've just tested it by disabling buffering on one of my IIS6 sites and with Fiddler2 I can see that it starts using chunked encoding for the responses. The defaults for IIS 7 don't appear to have changed, *but* you will get chunked encoding if you have enabled dynamic compression. It appears that the default for the doDynamicCompression attribute was changed in IIS 7.5 from false to true. http://www.iis.net/ConfigReference/system.webServer/urlCompression note that under the Compatibility section this page states that the default value was changed from false to true as of IIS 7.5, yet under the Configuration section further down the page states that the default value was true in IIS 7 and false in IIS 7.5, however the text above that statement is the reverse. Are you definitely running IIS 7? Or are you actually running IIS 7.5? -- Dan |