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dotnet xml : Exception on XmlDocumet.Load()
Hi,
I have xml files which contain a <!DOCTYPE> with a link to a dtd. On my local computer this this link is invalid as it refers to a folder that does not exist. The link has the format "file://localhost...". Using an System.Xml.XmlDocument object and calling the Load() function, the parses hangs for about 5 minutes and then thows an Exception with the text "the semaphore timeout period has expired". As the MSDN states the XmlDocument.Load() method does not do dtd validation so I wonder what is happening. Does the parser try to load the dtd file and gets a network timeout? Are there any switches in XmlDocument that I can use to ignore the dtd? Thanks,
[quoted text, click to view] Chris wrote: [quoted text, click to view] > Are there any switches in XmlDocument that I can use to ignore the dtd? You would need to assign an XmlResolver that returns null for any URL passed in e.g. (pseudo code) class DummyResolver : XmlUrlResolver { public override Uri ResolveUri (Uri baseUri, String relativeUri) { return null; } } XmlDocument xmlDocument = new XmlDocument(); xmlDocument.XmlResolver = new DummyResolver(); xmlDocument.Load(@"whatever.xml"); But you need to be aware that a DTD is not only necessary for validation but can also be needed to resolve entity references. And the behavior of XmlDocument and its XmlResolver depends on different factors, see <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> -- Martin Honnen
Hi,
Instead of returing 'null' from DummyResolver.ResolveUri(), try returning an empty stream from DummyResolver.GetEntity() whenever you get a resolution request for any uri that you don't want resolved. This should solve your problem. Ion [quoted text, click to view] "Martin Honnen" <mahotrash@yahoo.de> wrote in message <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/htmlnews:%23v98ucwLFHA.656@TK2MSFTNGP14.phx.gbl... > > > Chris wrote: > > > > using your suggested method seems the right way. > > Doing so, I get an Exception "object reference not set to an instance of > > an object" as soon as I 'return null' in the overridden method. > > The ResolveUri function is also often called with the document parsed, > > but with an empty baseUri. So I think that the baseUri is only != null > > when the parser tries to resolve a link. So I tried: > > > > if( baseUri != null ) > > return null; > > else > > return base.ResolveUri( baseUri, relativeUri ); > > > > But as soon as I return null I get the above mentioned error. > > Any suggestions? > > I am not sure how to solve that, looking at the documentation I had > hoped my suggestion would work out but it seems it doesn't, the > documentation here > /frlrfsystemxmlxmlresolverclassresolveuritopic.asp> [quoted text, click to view] > explicitly says: "Return Value > A Uri representing the absolute URI or a null reference (Nothing in > Visual Basic) if the relative URI can not be resolved." > Therefore I hoped if the resolver returns null the code calling it would > not further try to deal with the URI and simply ignore it and not try to > load it but that is not the case it seems. > > > -- > > Martin Honnen > http://JavaScript.FAQTs.com/
Hi,
Instead of returning 'null' from ResolveUri(), return an empty stream from GetEntity() whenever you get a resolution request for the known 'bad' uris. Regards, Ion [quoted text, click to view] "Chris" <chrismc912@hotmail.com> wrote in message <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/htmlnews:OJDI$1vLFHA.1884@TK2MSFTNGP15.phx.gbl... > Thanks for your reply, > using your suggested method seems the right way. > Doing so, I get an Exception "object reference not set to an instance of > an object" as soon as I 'return null' in the overridden method. > The ResolveUri function is also often called with the document parsed, > but with an empty baseUri. So I think that the baseUri is only != null > when the parser tries to resolve a link. So I tried: > > if( baseUri != null ) > return null; > else > return base.ResolveUri( baseUri, relativeUri ); > > But as soon as I return null I get the above mentioned error. > Any suggestions? > Thanks, > Chris > > Martin Honnen wrote: > > > > > > Chris wrote: > > > > > >> Are there any switches in XmlDocument that I can use to ignore the dtd? > > > > > > You would need to assign an XmlResolver that returns null for any URL > > passed in e.g. (pseudo code) > > > > class DummyResolver : XmlUrlResolver { > > public override Uri ResolveUri (Uri baseUri, String relativeUri) { > > return null; > > } > > } > > > > XmlDocument xmlDocument = new XmlDocument(); > > xmlDocument.XmlResolver = new DummyResolver(); > > > > xmlDocument.Load(@"whatever.xml"); > > > > But you need to be aware that a DTD is not only necessary for validation > > but can also be needed to resolve entity references. > > > > And the behavior of XmlDocument and its XmlResolver depends on different > > factors, see > > /frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> [quoted text, click to view] > > > >
Thanks for your reply,
using your suggested method seems the right way. Doing so, I get an Exception "object reference not set to an instance of an object" as soon as I 'return null' in the overridden method. The ResolveUri function is also often called with the document parsed, but with an empty baseUri. So I think that the baseUri is only != null when the parser tries to resolve a link. So I tried: if( baseUri != null ) return null; else return base.ResolveUri( baseUri, relativeUri ); But as soon as I return null I get the above mentioned error. Any suggestions? Thanks, Chris [quoted text, click to view] Martin Honnen wrote:
> > > Chris wrote: > > >> Are there any switches in XmlDocument that I can use to ignore the dtd? > > > You would need to assign an XmlResolver that returns null for any URL > passed in e.g. (pseudo code) > > class DummyResolver : XmlUrlResolver { > public override Uri ResolveUri (Uri baseUri, String relativeUri) { > return null; > } > } > > XmlDocument xmlDocument = new XmlDocument(); > xmlDocument.XmlResolver = new DummyResolver(); > > xmlDocument.Load(@"whatever.xml"); > > But you need to be aware that a DTD is not only necessary for validation > but can also be needed to resolve entity references. > > And the behavior of XmlDocument and its XmlResolver depends on different > factors, see > <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> >
[quoted text, click to view] Chris wrote: [quoted text, click to view] > using your suggested method seems the right way. > Doing so, I get an Exception "object reference not set to an instance of > an object" as soon as I 'return null' in the overridden method. > The ResolveUri function is also often called with the document parsed, > but with an empty baseUri. So I think that the baseUri is only != null > when the parser tries to resolve a link. So I tried: > > if( baseUri != null ) > return null; > else > return base.ResolveUri( baseUri, relativeUri ); > > But as soon as I return null I get the above mentioned error. > Any suggestions? I am not sure how to solve that, looking at the documentation I had hoped my suggestion would work out but it seems it doesn't, the documentation here <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemxmlxmlresolverclassresolveuritopic.asp> explicitly says: "Return Value A Uri representing the absolute URI or a null reference (Nothing in Visual Basic) if the relative URI can not be resolved." Therefore I hoped if the resolver returns null the code calling it would not further try to deal with the URI and simply ignore it and not try to load it but that is not the case it seems. -- Martin Honnen
Hi Ion,
thanks a lot for your reply. As I am quite new to .net I am not sure what type of System.IO.Stream object to retun. Can you give me an example of an empty stream? Thanks, Chris [quoted text, click to view] Ion Vasilian wrote:
> Hi, > > Instead of returning 'null' from ResolveUri(), return an empty stream > from GetEntity() whenever you get a resolution request for the known > 'bad' uris. Regards, > > Ion > > "Chris" <chrismc912@hotmail.com> wrote in message > news:OJDI$1vLFHA.1884@TK2MSFTNGP15.phx.gbl... > >>Thanks for your reply, >>using your suggested method seems the right way. >>Doing so, I get an Exception "object reference not set to an instance of >>an object" as soon as I 'return null' in the overridden method. >>The ResolveUri function is also often called with the document parsed, >>but with an empty baseUri. So I think that the baseUri is only != null >>when the parser tries to resolve a link. So I tried: >> >>if( baseUri != null ) >> return null; >>else >> return base.ResolveUri( baseUri, relativeUri ); >> >>But as soon as I return null I get the above mentioned error. >>Any suggestions? >>Thanks, >>Chris >> >>Martin Honnen wrote: >> >>> >>>Chris wrote: >>> >>> >>> >>>>Are there any switches in XmlDocument that I can use to ignore the dtd? >>> >>> >>>You would need to assign an XmlResolver that returns null for any URL >>>passed in e.g. (pseudo code) >>> >>>class DummyResolver : XmlUrlResolver { >>> public override Uri ResolveUri (Uri baseUri, String relativeUri) { >>> return null; >>> } >>>} >>> >>>XmlDocument xmlDocument = new XmlDocument(); >>>xmlDocument.XmlResolver = new DummyResolver(); >>> >>>xmlDocument.Load(@"whatever.xml"); >>> >>>But you need to be aware that a DTD is not only necessary for validation >>>but can also be needed to resolve entity references. >>> >>>And the behavior of XmlDocument and its XmlResolver depends on different >>>factors, see >>> > > <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html > /frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> > >>> >
Hi,
Here's the code that should do the trick: class DummyResolver : XmlUrlResolver { .... public override object GetEntity(Uri absoluteUri, string role, Type ofObjectToReturn) { if (absoluteUri != null && absoluteUri.AbsoluteUri == "<whatever you want to override>") { if (ofObjectToReturn == null || ofObjectToReturn == typeof(System.IO.Stream)) { return Stream.Null; } } return base.GetEntity(absoluteUri, role, ofObjectToReturn); } Regards, Ion [quoted text, click to view] "Chris" <chrismc912@hotmail.com> wrote in message news:OsDZR4$LFHA.3632@TK2MSFTNGP10.phx.gbl... > Hi Ion, > thanks a lot for your reply. As I am quite new to .net I am not sure > what type of System.IO.Stream object to retun. Can you give me an > example of an empty stream? > > Thanks, > Chris > > Ion Vasilian wrote: > > Hi, > > > > Instead of returning 'null' from ResolveUri(), return an empty stream > > from GetEntity() whenever you get a resolution request for the known > > 'bad' uris. Regards, > > > > Ion > > > > "Chris" <chrismc912@hotmail.com> wrote in message > > news:OJDI$1vLFHA.1884@TK2MSFTNGP15.phx.gbl... > > > >>Thanks for your reply, > >>using your suggested method seems the right way. > >>Doing so, I get an Exception "object reference not set to an instance of > >>an object" as soon as I 'return null' in the overridden method. > >>The ResolveUri function is also often called with the document parsed, > >>but with an empty baseUri. So I think that the baseUri is only != null > >>when the parser tries to resolve a link. So I tried: > >> > >>if( baseUri != null ) > >> return null; > >>else > >> return base.ResolveUri( baseUri, relativeUri ); > >> > >>But as soon as I return null I get the above mentioned error. > >>Any suggestions? > >>Thanks, > >>Chris > >> > >>Martin Honnen wrote: > >> > >>> > >>>Chris wrote: > >>> > >>> > >>> > >>>>Are there any switches in XmlDocument that I can use to ignore the dtd? > >>> > >>> > >>>You would need to assign an XmlResolver that returns null for any URL > >>>passed in e.g. (pseudo code) > >>> > >>>class DummyResolver : XmlUrlResolver { > >>> public override Uri ResolveUri (Uri baseUri, String relativeUri) { > >>> return null; > >>> } > >>>} > >>> > >>>XmlDocument xmlDocument = new XmlDocument(); > >>>xmlDocument.XmlResolver = new DummyResolver(); > >>> > >>>xmlDocument.Load(@"whatever.xml"); > >>> > >>>But you need to be aware that a DTD is not only necessary for validation > >>>but can also be needed to resolve entity references. > >>> > >>>And the behavior of XmlDocument and its XmlResolver depends on different > >>>factors, see > >>> > > > > <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html > > /frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> > > > >>> > > > >
Hi Ion,
thanks a lot for your help! Regads, Chris [quoted text, click to view] Ion Vasilian wrote:
> Hi, > > Here's the code that should do the trick: > > class DummyResolver : XmlUrlResolver { > ... > public override object GetEntity(Uri absoluteUri, string role, Type > ofObjectToReturn) { > if (absoluteUri != null && absoluteUri.AbsoluteUri == "<whatever you want > to override>") { > if (ofObjectToReturn == null || ofObjectToReturn == > typeof(System.IO.Stream)) { > return Stream.Null; > } > } > return base.GetEntity(absoluteUri, role, ofObjectToReturn); > } > > Regards, > Ion > > "Chris" <chrismc912@hotmail.com> wrote in message > news:OsDZR4$LFHA.3632@TK2MSFTNGP10.phx.gbl... > >>Hi Ion, >>thanks a lot for your reply. As I am quite new to .net I am not sure >>what type of System.IO.Stream object to retun. Can you give me an >>example of an empty stream? >> >>Thanks, >>Chris >> >>Ion Vasilian wrote: >> >>>Hi, >>> >>>Instead of returning 'null' from ResolveUri(), return an empty stream >>>from GetEntity() whenever you get a resolution request for the known >>>'bad' uris. Regards, >>> >>>Ion >>> >>>"Chris" <chrismc912@hotmail.com> wrote in message >>>news:OJDI$1vLFHA.1884@TK2MSFTNGP15.phx.gbl... >>> >>> >>>>Thanks for your reply, >>>>using your suggested method seems the right way. >>>>Doing so, I get an Exception "object reference not set to an instance of >>>>an object" as soon as I 'return null' in the overridden method. >>>>The ResolveUri function is also often called with the document parsed, >>>>but with an empty baseUri. So I think that the baseUri is only != null >>>>when the parser tries to resolve a link. So I tried: >>>> >>>>if( baseUri != null ) >>>> return null; >>>>else >>>> return base.ResolveUri( baseUri, relativeUri ); >>>> >>>>But as soon as I return null I get the above mentioned error. >>>>Any suggestions? >>>>Thanks, >>>>Chris >>>> >>>>Martin Honnen wrote: >>>> >>>> >>>>>Chris wrote: >>>>> >>>>> >>>>> >>>>> >>>>>>Are there any switches in XmlDocument that I can use to ignore the > > dtd? > >>>>> >>>>>You would need to assign an XmlResolver that returns null for any URL >>>>>passed in e.g. (pseudo code) >>>>> >>>>>class DummyResolver : XmlUrlResolver { >>>>> public override Uri ResolveUri (Uri baseUri, String relativeUri) { >>>>> return null; >>>>> } >>>>>} >>>>> >>>>>XmlDocument xmlDocument = new XmlDocument(); >>>>>xmlDocument.XmlResolver = new DummyResolver(); >>>>> >>>>>xmlDocument.Load(@"whatever.xml"); >>>>> >>>>>But you need to be aware that a DTD is not only necessary for > > validation > >>>>>but can also be needed to resolve entity references. >>>>> >>>>>And the behavior of XmlDocument and its XmlResolver depends on > > different > >>>>>factors, see >>>>> >>> >>> > <http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html > >>>/frlrfSystemXmlXmlDocumentClassXmlResolverTopic.asp> >>> >>> >
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