What is the fastest way to combine two xml files into one

Question

If I have two string of xml1 and xml2 which both represent xml in the same format. What is the fastest way to combine these together? The format is not important, but I just want to know how can I get rid off or ?

xml1 :

<?xml version="1.0" encoding="utf-8"?>
<AllNodes>
   <NodeA>
      <NodeB>test1</NodeB>
      <NodeB>test2</NodeB>
   </NodeA>
</AllNodes>

xm2 :

<?xml version="1.0" encoding="utf-8"?>
<AllNodes>
   <NodeA>
      <NodeB>test6</NodeB>
      <NodeB>test7</NodeB>
   </NodeA>
   <NodeA>
      <NodeB>test99</NodeB>
      <NodeB>test23</NodeB>
   </NodeA>
</AllNodes>

and have something like this :

<?xml version="1.0" encoding="utf-8"?>
    <AllNodes>
          <NodeA>
              <NodeB>test1</NodeB>
              <NodeB>test2</NodeB>
          </NodeA>
         <NodeA>
              <NodeB>test6</NodeB>
              <NodeB>test7</NodeB>
           </NodeA>
           <NodeA>
              <NodeB>test99</NodeB>
              <NodeB>test23</NodeB>
           </NodeA>
    </AllNodes>

Answer 1

If I were doing this (using C#), I would create a class that I can deserialize this XML to (you can use xsd.exe to do this), and then loop through all the nodes in the object representing the first piece of XML and "Add" them to the AllNodes property of the object representing the second XML.

Then serialize the second class back out the XML, and it should look like your 3rd example.

Answer 2

You have two basic options:

1. Parse the xml, combine the data structures, serialize back to xml.

2. If you know the structure, use some basic string manipulation to hack it. For example, in the example above you could take the inside of allnodes in the two xml blocks and put them in a single allnodes block and be done.

Answer 3

An XSLT transformation could do it:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"&gt;
  <xsl:param name="pXml1" select="''" />
  <xsl:param name="pXml2" select="''" />
  <xsl:param name="pRoot" select="'root'" />

  <xsl:template match="/">
    <xsl:variable name="vXml1" select="document($pXml1)" />
    <xsl:variable name="vXml2" select="document($pXml2)" />

    <xsl:element name="{$pRoot}">
      <xsl:copy-of select="$vXml1/*/*" />
      <xsl:copy-of select="$vXml2/*/*" />
    </xsl:element>
  </xsl:template>

</xsl:stylesheet>

Pass in the names of the files as parameters, as well as the name of the new root element.

Apply to any XML document, e.g. an empty one.

Answer 4

If you can guarantee this format you can combine them by doing string manipulation:

• Read the first file, keep everything before "</AllNodes>"
• Read the second file, remove the part up to "<AllNodes>"
• Combine those strings.

This should be the fastest way since no parsing is needed.

const string RelevantTag = "AllNodes";

string xml1 = File.ReadAllText(xmlFile1);
xml1 = xml1.Substring(0, xml.LastIndexOf("</" + RelevantTag + ">"));

string xml2 = File.ReadAllText(xmlFile2);
xml2 = xml2.Substring(xml.IndexOf("<" + RelevantTag + ">") + "<" + RelevantTag + ">".Length, xml1.Length);

File.WriteAllText(xmlFileCombined, xm1 + xml2);

That said I would always prefer the safe way to the fast way.

Answer 5

The easiest way to do this is using LINQ to XML. You can use either Union or Concat depending on your needs.

var xml1 = XDocument.Load("file1.xml");
var xml2 = XDocument.Load("file2.xml");

//Combine and remove duplicates
var combinedUnique = xml1.Descendants("AllNodes")
                          .Union(xml2.Descendants("AllNodes"));

//Combine and keep duplicates
var combinedWithDups = xml1.Descendants("AllNodes")
                           .Concat(xml2.Descendants("AllNodes"));

Answer 6

Since you asked for the fastest:

If (and only if) the xml structure is always consistent: (this is pseudo code)

string xml1 = //get xml1 somehow
string xml2 = //get xml2 somehow
xml1 = replace(xml1, "<?xml version=\"1.0\" encoding=\"utf-8\"?>", "");
xml1 = replace(xml1, "<allnodes>", "");
xml1 = replace(xml1, "</allnodes>", "");
xml2 = replace(xml2, "<allnodes>", "<allnodes>\n" + xml1);

It's a giant hack but it's fast. Expect to see it on TheDailyWTF when your colleagues find it.

Answer 7

If you want to use the XmlDocument, try this

 var lNode = lDoc1.ImportNode(lDoc2.DocumentElement.FirstChild, true);
 lDoc1.DocumentElement.AppendChild(lNode);