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POAn error has occurred opening extern DTD (w3.org, xhtml1-transitional.dtd). 503 Server Unavailable
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copied!<p>I'm trying to do xpath queries over an xhtml document. Using .NET 3.5.</p> <p>The document looks like this: </p> <pre><code><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en" xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> .... </head> <body> ... </body> </html> </code></pre> <p>Because the document includes various char entities (<code>&nbsp;</code> and so on), I need to use the DTD, in order to load it with an <a href="http://msdn.microsoft.com/en-us/library/system.xml.xmlreader.aspx" rel="nofollow noreferrer">XmlReader</a>. So my code looks like this: </p> <pre><code>var s = File.OpenRead(fileToRead) var reader = XmlReader.Create(s, new XmlReaderSettings{ ProhibitDtd=false }); </code></pre> <p>But when I run this, it returns</p> <blockquote> <p>An error has occurred while opening external DTD '<a href="http://www.w3.org/TR/xhtml1-transitional.dtd" rel="nofollow noreferrer">http://www.w3.org/TR/xhtml1-transitional.dtd</a>': The remote server returned an error: (503) Server Unavailable. </p> </blockquote> <p>Now, I know <em>why</em> I am getting the 503 error. <a href="http://www.w3.org/blog/systeam/2008/02/08/w3c_s_excessive_dtd_traffic" rel="nofollow noreferrer">W3C explained it very clearly</a>. </p> <p>I've seen "workarounds" where people just disable the DTD. This is what <code>ProhibitDtd=true</code> can do, and it eliminates the 503 error. </p> <p>But in my case that leads to other problems - the app doesn't get the entity defintions and so isn't well-formed XML. How can I validate with the DTD, and get the entity definitions, without hitting the w3.org website? </p> <hr> <p>I think .NET 4.0 has a nifty built-in capability to handle this situation: the <a href="http://msdn.microsoft.com/en-us/library/system.xml.resolvers.xmlpreloadedresolver(VS.95).aspx" rel="nofollow noreferrer">XmlPreloadedResolver</a>. But I need a solution for .NET 3.5. </p> <hr> <p>related:<br> - <a href="https://stackoverflow.com/questions/2502581">java.io.IOException: Server returned HTTP response code: 503</a> </p>

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