CODEWITHSUNDEEP
c#.netxmlschemaxml-namespaces
Stephen Falken
Stephen Falken

Reputation: 111

Namespaces, Schemas, Elements and Attributes in an XmlDocument in .NET

I'm putting this here because I saw a lot of Q&A for XML on StackOverflow while trying to solve my own problems, and figured that once I'd found it, I'd post what I found so when someone else needs some XML help, this might help them.

My goal: To create an XML document that contains the following XML Declaration, Schema & Namespace Information:

<?xml version="1.0" encoding="UTF-8"?>
<abc:abcXML xsi:schemaLocation="urn:abcXML:v12 http://www.test.com/XML/schemas/v12/abcXML_v12.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ase="urn:abcXML:v12">

I'd already done it in Python for a quick prototype using minidom, and it was very simple. I needed to do it in a .NET language though (C#), because that's what the business calls for. I'm quite familiar with C#, but I've always stayed away from processing XML with it because I honestly don't have an in-depth grasp of XML and it's guidelines. Today, I had to face my demons.

Upvotes: 0

Views: 403

Answers (2)

jdweng
jdweng

Reputation: 34419

For complicated namespaces it is simpler to just parse the xml string. I like using xml linq. You sample xml is wrong. The namespace is "ase" (not abc).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
                "<ase:abcXML xsi:schemaLocation=\"urn:abcXML:v12 http://www.test.com/XML/schemas/v12/abcXML_v12.xsd\"" +
                   " xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"" +
                   " xmlns:ase=\"urn:abcXML:v12\">" +
                "</ase:abcXML>";

            XDocument doc = XDocument.Parse(xml);

            XElement root = doc.Root;
            XNamespace nsAse = root.GetNamespaceOfPrefix("ase");
        }
    }
}

Upvotes: 0

Stephen Falken
Stephen Falken

Reputation: 111

Here's how I did it:

The first part is simple enough - create a document, and create a DocumentElement for the root (there's a catch here which I get to later):

XmlDeclaration xmlDeclaration = doc.CreateXmlDeclaration("1.0", "UTF-8", null);
XmlElement root = doc.DocumentElement;
doc.InsertBefore(xmlDeclaration, root);

The next part seems simple enough - create an element, give it a prefix, name and URI, then append it to the document. I thought this would work, but it doesn't (this is where the minimal understanding of XML comes into play):

XmlElement abcXML = xmlDoc.CreateElement("ase", "abcXML", "urn:abcXML:r38 http://www.w3.org/2001/XMLSchema-instance");
XmlAttribute xmlAttr = xmlDoc.CreateAttribute("xsi:schemaLocation", "urn:abcXML:v12 http://www.test.com/XML/schemas/v12/abcXML_v12.xsd");
abcXML.AppendChild(xmlAttr);
xmlDoc.AppendChild(abcXML);

I tried to use doc.LoadXml() and doc.CreateDocumentFragment() and write my own declarations. No - I would get "Unexpected end of file". For those interested in XmlDocumentFragment: https://learn.microsoft.com/en-us/dotnet/api/system.xml.xmldocumentfragment.innerxml?view=netcore-3.1

This Microsoft article about XML Schemas and Namespaces didn't directly help me: https://learn.microsoft.com/en-us/dotnet/standard/data/xml/including-or-importing-xml-schemas

After doing more reading on XML, and going through the documentation for XmlDocument, XmlElement and XmlAttribute, this is the solution:

XmlElement abcXML = xmlDoc.CreateElement("ase", "abcXML", "urn:abcXML:r38");
XmlAttribute xmlAttr = xmlDoc.CreateAttribute("xsi:schemaLocation", "http://www.w3.org/2001/XMLSchema-instance");
xmlAttr.InnerXml = "urn:abcXML:v12 http://www.test.com/XML/schemas/v12/abcXML_v12.xsd";
abcXML.Attributes.Append(xmlAttr);
xmlDoc.AppendChild(abcXML);

Now you can add the elements to your document like so:

XmlElement header = doc.CreateElement(string.Empty, "Header", string.Empty);
abcXML.AppendChild(header);

To save the document, I used:

xmlDoc.Save(fileLocation);

I compared my output to the sample I had, and after comparing the file contents, I had succeeded in matching it. I provided the output to the client, they uploaded it into application they were using, and it failed: Row 1, Column 1 - Unexpected Character.

I had a suspicion it was encoding, and I was right. Using xmlDoc.Save(fileLocation) is correct, but it generates a UTF-8 file with the Byte Order Mark (BOM) at Row 1, Column 1. The XML parsing function in the application doesn't expect that, so the process failed. To fix that, I used the following method:

Encoding enc = new UTF8Encoding(false); /* This creates a UTF-8 encoding without the BOM */
using (System.IO.TextWriter tw = new System.IO.StreamWriter(filePath, false, enc))
{
    xmlDoc.Save(tw);
}
return true;

I generated the file again, sent it to the client, and it worked first go.

I hope someone finds this to be useful.

Upvotes: 1

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