使用 xmlReader 过滤 C# 中特定元素值的大 XML [英] Filter Large XML for specific element value in C# Using xmlReader

问题描述

在这个线程中:在 C# 中过滤特定元素值的 XML

我能够使用 XDocument 过滤 xml 文件以查找特定元素.但是，对于巨大的 xml 文件，XDocument 似乎不是一个可行的解决方案，因为它失败并显示 System.OutOfMemoryException 消息.仔细研究，看起来 xmlReader 在处理大型 xmls 时内存效率更高.

如何重写接受的答案，使用xmlReader，以获得相同的结果?

解决方案

请尝试以下解决方案.

它具有很强的可扩展性，可以毫无问题地处理多 GB 大小的 XML 文件.

XStreamingElement 使用了一种扩展方法，该方法使用 XmlReader<流式传输由

Section 1

节点过滤的源 XML/代码>.

c#

void Main(){const string inputXMLFile = @e:\Temp\Sanosi.xml";const string outputXMLFile = @e:\Temp\Sanosi_Streamed.xml";const string ROW =条目"；const string FILTER = "Section 1";//将 XML 流式传输到文件系统System.Diagnostics.Stopwatch timer = new System.Diagnostics.Stopwatch();定时器开始()；//形状输出 XMLXStreamingElement newXML = new XStreamingElement("root",来自 StreamElements(inputXMLFile, ROW) 中的元素.Where(x => x.Element(section").Value.Equals(FILTER))select new XElement(ROW, element.Elements("image")));newXML.Save(outputXMLFile, SaveOptions.OmitDuplicateNamespaces);FileInfo fileBefore = new FileInfo(inputXMLFile);FileInfo fileAfter = new FileInfo(outputXMLFile);定时器.停止()；Console.WriteLine("Streamed XML file '{0}', {1} bytes to file system as: '{2}', {3} bytes{5}Elapsed time: {4}",fileBefore.FullName, fileBefore.Length, fileAfter.FullName, fileAfter.Length, timer.Elapsed, 环境.NewLine);}私有静态 IEnumerable流元素(字符串文件名，字符串元素名){使用 (var rdr = XmlReader.Create(fileName)){rdr.MoveToContent();而 (rdr.Read()){if ((rdr.NodeType == XmlNodeType.Element) && (rdr.Name == elementName)){var e = XElement.ReadFrom(rdr) as XElement;收益率e；}}rdr.关闭();}}

In this thread: Filter XML for specific element value in C#

I was able to filter xml files to look for specific elements using XDocument. However, with huge xml files, it seems XDocument is not a feasible solution as it fails with System.OutOfMemoryException message. Digging around, it looks like xmlReader is more memory efficient when handling large xmls.

How to re-write the accepted answer, to use xmlReader, to get the same result?

解决方案

Please try the following solution.

It is very scalable and can process multi GB size XML files without any problem.

The XStreamingElement is using an extension method that streams the source XML filtered by a <section>Section 1</section> node using an XmlReader.

c#

void Main()
{
    const string inputXMLFile = @"e:\Temp\Sanosi.xml";
    const string outputXMLFile = @"e:\Temp\Sanosi_Streamed.xml";
    const string ROW = "Entry";
    const string FILTER = "Section 1";

    // Stream XML to file system
    System.Diagnostics.Stopwatch timer = new System.Diagnostics.Stopwatch();
    timer.Start();

    // Shape output XML
    XStreamingElement newXML = new XStreamingElement("root",
       from element in StreamElements(inputXMLFile, ROW)
            .Where(x => x.Element("section").Value.Equals(FILTER))
       select new XElement(ROW, element.Elements("image")
          ));

    newXML.Save(outputXMLFile, SaveOptions.OmitDuplicateNamespaces);

    FileInfo fileBefore = new FileInfo(inputXMLFile);
    FileInfo fileAfter = new FileInfo(outputXMLFile);

    timer.Stop();

    Console.WriteLine("Streamed XML file '{0}', {1} bytes to file system as: '{2}', {3} bytes{5}Elapsed time: {4}",
      fileBefore.FullName
      , fileBefore.Length
      , fileAfter.FullName
      , fileAfter.Length
      , timer.Elapsed
      , Environment.NewLine);
}

private static IEnumerable<XElement> StreamElements(string fileName, string elementName)
{
    using (var rdr = XmlReader.Create(fileName))
    {
        rdr.MoveToContent();
        while (rdr.Read())
        {
            if ((rdr.NodeType == XmlNodeType.Element) && (rdr.Name == elementName))
            {
                var e = XElement.ReadFrom(rdr) as XElement;
                yield return e;
            }
        }
        rdr.Close();
    }
}

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