blocks|key|2481619|text|在ReadOuterXml()中获得OutOfMemoryException的最有可能的原因是，您试图将1+GB的XML文档中的很大一部分读入到字符串中，并且命中Maximum+string+length+in+.Net。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2481620|所以，不要这样做。使用XDocument.Load()和XmlReader.ReadSubtree()直接从XmlReader加载|2481621|using+(var+xr+=+XmlReader.Create(fileName))
{
++++while+(xr.Read()+&&+success)
++++{
++++++++if+(xr.NodeType+!=+XmlNodeType.Element)
++++++++++++continue;
++++++++switch+(xr.Name)
++++++++{
++++++++++++case+"A":
++++++++++++++++{
++++++++++++++++++++//+ReadSubtree()+positions+the+reader+at+the+EndElement+of+the+element+read,+so+the+
++++++++++++++++++++//+next+call+to+Read()+moves+to+the+next+node.
++++++++++++++++++++using+(var+subReader+=+xr.ReadSubtree())
++++++++++++++++++++{
++++++++++++++++++++++++var+doc+=+XDocument.Load(subReader);
++++++++++++++++++++++++GetDetails(doc);
++++++++++++++++++++}
++++++++++++++++}
++++++++++++++++break;
++++++++}
++++}
}|code-block|syntax|javascript|2481622|然后在GetDetails()中执行以下操作：|2481623|private+int+GetDetails(XDocument+rootDocument)
{
++++var+xnodes+=+rootDocument.XPathSelectElements("//A/B").ToList();
++++//Then++working+on+list+of+nodes
++++return+xnodes.Count;
}|2481624|这不仅会使用更少的内存，而且还会有更高的性能。ReadOuterXml()使用临时XmlWriter将输入流中的XML复制到输出StringWriter+(然后对其进行第二次解析)。这个版本的算法完全跳过了这个额外的工作。它还避免了创建足够大的字符串以在large+object+heap上运行，这可能会导致额外的性能问题。|2481625|如果这仍然使用了太多的内存，那么您将需要为您的实现SAX-like解析，一次只加载一个元素。首先，介绍下面的扩展方法：|2481626|public+static+partial+class+XmlReaderExtensions
{
++++public+static+IEnumerable<XElement>+WalkXmlElements(this+XmlReader+xmlReader,+Predicate<Stack<XName>>+filter)
++++{
++++++++Stack<XName>+names+=+new+Stack<XName>();

++++++++while+(xmlReader.Read())
++++++++{
++++++++++++if+(xmlReader.NodeType+==+XmlNodeType.Element)
++++++++++++{
++++++++++++++++names.Push(XName.Get(xmlReader.LocalName,+xmlReader.NamespaceURI));
++++++++++++++++if+(filter(names))
++++++++++++++++{
++++++++++++++++++++using+(var+subReader+=+xmlReader.ReadSubtree())
++++++++++++++++++++{
++++++++++++++++++++++++yield+return+XElement.Load(subReader);
++++++++++++++++++++}
++++++++++++++++}
++++++++++++}

++++++++++++if+((xmlReader.NodeType+==+XmlNodeType.Element+&&+xmlReader.IsEmptyElement)
++++++++++++++++%7C%7C+xmlReader.NodeType+==+XmlNodeType.EndElement)
++++++++++++{
++++++++++++++++names.Pop();
++++++++++++}
++++++++}
++++}
}|2481627|然后，按如下方式使用它：|2481628|using+(var+xr+=+XmlReader.Create(fileName))
{
++++Predicate<Stack<XName>>+filter+=
++++++++(stack)+=>+stack.Peek().LocalName+==+"B"+&&+stack.Count+>+1+&&+stack.ElementAt(1).LocalName+==+"A";
++++foreach+(var+element+in+xr.WalkXmlElements(filter))
++++{
++++++++//Then+working+on+the+specific+node.
++++}
}|2481629|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/140468|1|https://msdn.microsoft.com/en-us/library/bb356384(v=vs.110).aspx|2|https://msdn.microsoft.com/en-us/library/system.xml.xmlreader.readsubtree(v=vs.110).aspx)|3|http://referencesource.microsoft.com/#System.Xml/System/Xml/Core/XmlReader.cs,2e70466b502f4206,references|4|https://stackoverflow.com/q/8951836|5|https://en.wikipedia.org/wiki/Simple_API_for_XML^0|1|E|I|K|29|T|0|0|B|G|S|N|1I|9|B|G|1|S|N|2|0|0|3|C|0|0|N|E|15|9|1S|C|N|E|3|3J|H|4|0|19|3|P|8|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@$9|1N|A|1O|1|1P]]|E|$]]|$1|F|3|G|5|6|7|1Q|8|@$9|1R|A|1S|B|C]|$9|1T|A|1U|B|C]|$9|1V|A|1W|B|C]]|D|@$9|1X|A|1Y|1|1Z]|$9|20|A|21|1|22]]|E|$]]|$1|H|3|I|5|J|7|23|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|24|8|@$9|25|A|26|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|27|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|28|8|@$9|29|A|2A|B|C]|$9|2B|A|2C|B|C]|$9|2D|A|2E|B|C]]|D|@$9|2F|A|2G|1|2H]|$9|2I|A|2J|1|2K]]|E|$]]|$1|S|3|T|5|6|7|2L|8|@$9|2M|A|2N|B|C]]|D|@$9|2O|A|2P|1|2Q]]|E|$]]|$1|U|3|V|5|J|7|2R|8|@]|D|@]|E|$K|L]]|$1|W|3|X|5|6|7|2S|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|J|7|2T|8|@]|D|@]|E|$K|L]]|$1|10|3|-4|5|6|7|2U|8|@]|D|@]|E|$]]]|11|$12|$5|13|14|15|E|$16|17]]|18|$5|13|14|15|E|$16|19]]|1A|$5|13|14|15|E|$16|1B]]|1C|$5|13|14|15|E|$16|1D]]|1E|$5|13|14|15|E|$16|1F]]|1G|$5|13|14|15|E|$16|1H]]]]

The most likely reason you are getting a <code>OutOfMemoryException</code> in <code>ReadOuterXml()</code> is that you are trying to read in a substantial portion of the 1 GB XML document into a string, and are hitting the <a href="https://stackoverflow.com/q/140468">Maximum string length in .Net</a>.

So, don't do that. Instead load directly from the <code>XmlReader</code> using <a href="https://msdn.microsoft.com/en-us/library/bb356384(v=vs.110).aspx" rel="nofollow noreferrer"><code>XDocument.Load()</code></a> with <a href="https://msdn.microsoft.com/en-us/library/system.xml.xmlreader.readsubtree(v=vs.110).aspx" rel="nofollow noreferrer"><code>XmlReader.ReadSubtree()</code></a>:

<pre><code>using (var xr = XmlReader.Create(fileName))
{
 while (xr.Read() &amp;&amp; success)
 {
 if (xr.NodeType != XmlNodeType.Element)
 continue;
 switch (xr.Name)
 {
 case "A":
 {
 // ReadSubtree() positions the reader at the EndElement of the element read, so the 
 // next call to Read() moves to the next node.
 using (var subReader = xr.ReadSubtree())
 {
 var doc = XDocument.Load(subReader);
 GetDetails(doc);
 }
 }
 break;
 }
 }
}
</code></pre>

And then in <code>GetDetails()</code> do:

<pre><code>private int GetDetails(XDocument rootDocument)
{
 var xnodes = rootDocument.XPathSelectElements("//A/B").ToList();
 //Then working on list of nodes
 return xnodes.Count;
}
</code></pre>

Not only will this use less memory, it will also be more performant. <a href="http://referencesource.microsoft.com/#System.Xml/System/Xml/Core/XmlReader.cs,2e70466b502f4206,references" rel="nofollow noreferrer"><code>ReadOuterXml()</code></a> uses a temporary <code>XmlWriter</code> to copy the XML in the input stream to an output <code>StringWriter</code> (which you then parse a second time). This version of the algorithm completely skips this extra work. It also avoids creating strings large enough to go on the <a href="https://stackoverflow.com/q/8951836">large object heap</a> which can cause additional performance issues.

If this is still using too much memory you will need to implement <a href="https://en.wikipedia.org/wiki/Simple_API_for_XML" rel="nofollow noreferrer">SAX-like</a> parsing for your XML where you only load one element <code>&lt;B&gt;</code> at a time. First, introduce the following extension method:

<pre><code>public static partial class XmlReaderExtensions
{
 public static IEnumerable&lt;XElement&gt; WalkXmlElements(this XmlReader xmlReader, Predicate&lt;Stack&lt;XName&gt;&gt; filter)
 {
 Stack&lt;XName&gt; names = new Stack&lt;XName&gt;();

 while (xmlReader.Read())
 {
 if (xmlReader.NodeType == XmlNodeType.Element)
 {
 names.Push(XName.Get(xmlReader.LocalName, xmlReader.NamespaceURI));
 if (filter(names))
 {
 using (var subReader = xmlReader.ReadSubtree())
 {
 yield return XElement.Load(subReader);
 }
 }
 }

 if ((xmlReader.NodeType == XmlNodeType.Element &amp;&amp; xmlReader.IsEmptyElement)
 || xmlReader.NodeType == XmlNodeType.EndElement)
 {
 names.Pop();
 }
 }
 }
}
</code></pre>

Then, use it as follows:

<pre><code>using (var xr = XmlReader.Create(fileName))
{
 Predicate&lt;Stack&lt;XName&gt;&gt; filter =
 (stack) =&gt; stack.Peek().LocalName == "B" &amp;&amp; stack.Count &gt; 1 &amp;&amp; stack.ElementAt(1).LocalName == "A";
 foreach (var element in xr.WalkXmlElements(filter))
 {
 //Then working on the specific node.
 }
}
</code></pre>

blocks|key|24934|text|using+(var+reader+=+XmlReader.Create(fileName))
{+++
++++XmlDocument+oXml+=+new+XmlDocument();
++++while+(reader.Read())
++++++++{++++++++++++++++++
++++++++++++oXml.Load(reader);++++++++++++++++++++
++++++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|24935|对于我来说，上面的代码解决了我们通过XmlDocument+Load方法将其返回给XmlDocument时的问题|unstyled|24936|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>using (var reader = XmlReader.Create(fileName))
{ 
 XmlDocument oXml = new XmlDocument();
 while (reader.Read())
 { 
 oXml.Load(reader); 
 }
}
</code></pre>
For me above code resolved the issue when we return it to XmlDocument through XmlDocument Load method

I am working on a large XML file and while running the application, <code>XmlTextReader.ReadOuterXml()</code> method is throwing memory exception.

Lines of codes are like,

<pre><code>XmlTextReader xr = null;
try
{
 xr = new XmlTextReader(fileName);
 while (xr.Read() &amp;&amp; success)
 {
 if (xr.NodeType != XmlNodeType.Element) 
 continue;
 switch (xr.Name)
 {
 case "A":
 var xml = xr.ReadOuterXml();
 var n = GetDetails(xml);
 break;
 }
 }
}
catch (Exception ex)
{
 //Do stuff
}
</code></pre>

Using:

<pre><code>private int GetDetails (string xml)
{

 var rootNode = XDocument.Parse(xml);
 var xnodes = rootNode.XPathSelectElements("//A/B").ToList();
 //Then working on list of nodes

}
</code></pre>

Now while loading the XML files, the application throwing exception on the <code>xr.ReadOuterXml()</code> line. What can be done to avoid this? The size of XML is almost 1 GB.

ReadOuterXml is throwing OutOfMemoryException reading part of large (1 GB) XML file

我正在处理一个很大的XML文件，在运行应用程序时，XmlTextReader.ReadOuterXml()方法抛出了内存异常。代码行是这样的，XmlTextReader xr = null;try{    xr = new XmlTextReader(fileName);    while (xr.Read() && ...

问ReadOuterXml正在抛出OutOfMemoryException读取大(1 GB) XML文件的一部分
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