Split XML document apart creating multiple output

问题:

I need to take an XML file and create multiple output xml files from the repeating nodes of the input file. The source file "AnimalBatch.xml" looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<Animals>
<Animal id="1001">
<Quantity>One</Quantity>
<Adjective>Red</Adjective>
<Name>Rooster</Name>
</Animal>
<Animal id="1002">
<Quantity>Two</Quantity>
<Adjective>Stubborn</Adjective>
<Name>Donkeys</Name>
</Animal>
<Animal id="1003">
<Quantity>Three</Quantity>
<Color>Blind</Color>
<Name>Mice</Name>
</Animal>
</Animals>

The program needs to split the repeating "Animal" and produce 3 files named: Animal_1001.xml, Animal_1002.xml, and Animal_1003.xml

Each output file should contain just their respective element (which will be the root). The id attribute from AnimalsBatch.xml will supply the sequence number for the Animal_xxxx.xml filenames. The id attribute does not need to be in the output files.

---

Animal_1001.xml:
<?xml version="1.0" encoding="utf-8"?>
<Animal>
<Quantity>One</Quantity>
<Adjective>Red</Adjective>
<Name>Rooster</Name>
</Animal>

---

Animal_1002.xml
<?xml version="1.0" encoding="utf-8"?>
<Animal>
<Quantity>Two</Quantity>
<Adjective>Stubborn</Adjective>
<Name>Donkeys</Name>
</Animal>

---

Animal_1003.xml>
<?xml version="1.0" encoding="utf-8"?>
<Animal>
<Quantity>Three</Quantity>
<Adjective>Blind</Adjective>
<Name>Mice</Name>
</Animal>

I want to do this with XmlDocument, since it needs to be able to run on .Net 2.0.

My program looks like this:

    static void Main(string[] args)
    {
        string strFileName;    
        string strSeq;                    

        XmlDocument doc = new XmlDocument(); 
        doc.Load("D:\\Rick\\Computer\\XML\\AnimalBatch.xml");

        XmlNodeList nl = doc.DocumentElement.SelectNodes("Animal");

        foreach (XmlNode n in nl)
        {
            strSeq = n.Attributes["id"].Value;

            XmlDocument outdoc = new XmlDocument();
            XmlNode rootnode = outdoc.CreateNode("element", "Animal", "");

            outdoc.AppendChild(rootnode); // Put the wrapper element into outdoc

            outdoc.ImportNode(n, true);   // place the node n into outdoc
            outdoc.AppendChild(n);        // This statement errors:
            // "The node to be inserted is from a different document context."

            strFileName = "Animal_" + strSeq + ".xml";

            outdoc.Save(Console.Out);
            Console.WriteLine();
        }
        Console.WriteLine("END OF PROGRAM:  Press <ENTER>");
        Console.ReadLine();
    }

I think I have 2 problems.

A) After doing the ImportNode on node n into outdoc, I call outdoc.AppendChild(n) which complains: "The node to be inserted is from a different document context." I do not know if this is a scope issue referencing node n within the ForEach loop - or if I am somehow not using ImportNode() or AppendChild properly. 2nd argument on ImportNode() is set to true, because I want the child elements of Animal (3 fields arbitrarily named Quantity, Adjective, and Name) to end up in the destination file.

B) Second problem is getting the Animal element into outdoc. I'm getting '' but I need ' ' so I can place node n inside it. I think my problem is how I am doing: outdoc.AppendChild(rootnode);

To show the xml, I'm doing: outdoc.Save(Console.Out); I do have the code to save() to an output file - which does work, as long as I can get outdoc assembled properly.

There is a similar question at: Split XML in Multiple XML files, but I don't understand the solution code yet. I think I'm pretty close on this approach, and will appreciate any help you can provide.

I'm going to be doing this same task using XmlReader, since I'm going to need to be able to handle large input files, and I understand that XmlDocument reads the whole thing in and can cause memory issues.

回答1:

That's a simple method that seems what you are looking for

public void test_xml_split()
{
    XmlDocument doc = new XmlDocument();
    doc.Load("C:\\animals.xml");
    XmlDocument newXmlDoc = null;

    foreach (XmlNode animalNode in doc.SelectNodes("//Animals/Animal"))
    {
        newXmlDoc = new XmlDocument();
        var targetNode = newXmlDoc.ImportNode(animalNode, true);
        newXmlDoc.AppendChild(targetNode);
        newXmlDoc.Save(Console.Out);
        Console.WriteLine();
    }
}

回答2:

This approach seems to work without using the "var targetnode" statement. It creates an XmlNode object called targetNode from outdoc's "Animal" element in the ForEach loop. I think the main things that were problems in my original code were: A) I was getting nodelist nl incorrectly. And B) I couldn't "Import" node n, I think because it was associated specifically with doc. It had to be created as its own Node.

The problem with the prior proposed solution was the use of the "var" keyword. My program has to assume 2.0 and that came in with v3.0. I like Rogers solution, in that it is concise. For me - I wanted to do each thing as a separate statement.

    static void SplitXMLDocument() 
    {
        string strFileName;
        string strSeq;
        XmlDocument doc = new XmlDocument();             // The input file
        doc.Load("D:\\Rick\\Computer\\XML\\AnimalBatch.xml");
        XmlNodeList nl = doc.DocumentElement.SelectNodes("//Animals/Animal");

        foreach (XmlNode n in nl)
        {
            strSeq = n.Attributes["id"].Value;           // Animal nodes have an id attribute

            XmlDocument outdoc = new XmlDocument();      // Create the outdoc xml document
            XmlNode targetNode = outdoc.CreateElement("Animal"); // Create a separate node to hold the Animal element

            targetNode = outdoc.ImportNode(n, true);     // Bring over that Animal
            targetNode.Attributes.RemoveAll();           // Remove the id attribute in <Animal id="1001">

            outdoc.ImportNode(targetNode, true);         // place the node n into outdoc
            outdoc.AppendChild(targetNode);              // AppendChild to make it stick

            strFileName = "Animal_" + strSeq + ".xml";                
            outdoc.Save(Console.Out); Console.WriteLine();
            outdoc.Save("D:\\Rick\\Computer\\XML\\" + strFileName);
            Console.WriteLine();
        }
    }