Develop Reference

Creating an XML with multiple root elements

I'm trying to create an XML with multiple root elements. I can't change that because that is the way I'm supposed to send the XML to the server. This is the error I get when I try to run the code:
System.InvalidOperationException: This operation would create an incorrectly structured document.
Is there a way to overwrite this error and have it so that it ignores this?
Alright so let me explain this better:
Here is what I have
XmlDocument doc = new XmlDocument();
doc.LoadXml(_application_data);
Now that creates the XML document and I can add a fake root element to it so that it works. However, I need to get rid of that and convert it into a DocumentElement object.
How would I go about doing that?

Specify Fragment when creating XmlWriter as shown here
XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
settings.ConformanceLevel = ConformanceLevel.Fragment;
settings.CloseOutput = false;
// Create the XmlWriter object and write some content.
MemoryStream strm = new MemoryStream();
using (XmlWriter writer = XmlWriter.Create(strm, settings))
{
writer.WriteElementString("orderID", "1-456-ab");
writer.WriteElementString("orderID", "2-36-00a");
writer.Flush();
}

If it has multiple root elements, it's not XML. If it resembles XML in other ways, you could place everything under a root element, then when you send the string to the server, you just combine the serialized child elements of this root element, or as #Austin points out, use an inner XML method if available.

just create an XML with single root then get it's content as XML text.
you are talking about XML fragment anyways, since good xml has only one root.
this is sample to help you started:
var xml = new XmlDocument();
var root = xml.CreateElement("root");
root.AppendChild(xml.CreateElement("a"));
root.AppendChild(xml.CreateElement("b"));
Console.WriteLine(root.InnerXml); // outputs "<a /><b />"

XmlDocument in place transform with XSL

I'm sorry if this is an obvious question, but I'm getting abit frustrated trying to find an answer.
Can I perform an XSL transform on a loaded XmlDocument in place? That is, without having to create a writer to the document?
I ask because I have an XmlDocument binding inside a WPF app that I want to sort. The sorts can get a little complicated so XSL seemed a good fit. Here's the code that I'm stuck at:
XmlDataProvider xmlDP = (XmlDataProvider)this.Resources["ItemDB"];
string xsltPath = System.Configuration.ConfigurationManager.AppSettings["XSLDirextory"];
string path = xsltPath + "SortItemName.xslt";
if (System.IO.File.Exists(path))
{
XslCompiledTransform compTrans = new XslCompiledTransform();
compTrans.Load(path);
//compTrans.Transform(xmlDP.Document, new XsltArgumentList(), xmlDP.Document.XmlResolver);
}
After loading the transform, I'd like to just be able to compTrans(xmlDP.Document); or something that has the same effect. (to be clear, xmlDP.Document is an XmlDocument ) so that the XmlDocument has the result of the transform.
What's the best way to accomplish this?

The closest you can do is create a new XmlDocument with e.g.
XmlDocument result = new XmlDocument();
using (XmlWriter xw = result.CreateNavigator().AppendChild())
{
compTrans.Transform(xmlDP.Document, null, xw);
xw.Close();
}
and then assign that to your property:
xmlDP.Document = result;
Of course that requires that xmlDP.Document can be set.

XSLT always creates a new document to hold the transformation result, it never modifies the input document.

How to read an XML document in C# with a namespace that has no associated prefix

I am trying to read OSIS formatted documents. I have cut the document down to a simple fragment:
<?xml version="1.0" encoding="utf-8"?>
<osis xmlns="http://www.bibletechnologies.net/2003/OSIS/namespace">
<osisText osisRefWork="Bible" osisIDWork="kjv" xml:lang="en">
</osisText>
</osis>
I try to read it with this sample code from the MSDN documentation:
XPathDocument document = new XPathDocument("osis.xml");
XPathNavigator navigator = document.CreateNavigator();
XPathNodeIterator nodes = navigator.Select("/osis/osisText");
while (nodes.MoveNext())
{
Console.WriteLine(nodes.Current.Name);
}
The problem is that the selection contains no nodes and throws no exception. Since the code discards the root tag, I can't read the document. If I remove the xmlns="http://www.bibletechnologies.net/2003/OSIS/namespace" from the root osis tag, it works just fine. The offensive URL returns a 404 code, but otherwise I see nothing wrong with this XML. Can someone explain why this code won't read the document? What options do I have besides hand editing every document before trying to load it?

Your XPath expression is missing a namespace prefix.
The element that you're trying to select has a namespace URI of http://www.bibletechnologies.net/2003/OSIS/namespace, and XPath will not match these nodes using paths with an empty namespace URI.
I tested this revision in .NET 2.0 and it found the node as expected.
XPathDocument document = new XPathDocument("osis.xml");
XPathNavigator navigator = document.CreateNavigator();
XmlNamespaceManager xmlns = new XmlNamespaceManager(navigator.NameTable);
xmlns.AddNamespace("osis", "http://www.bibletechnologies.net/2003/OSIS/namespace");
XPathNodeIterator nodes = navigator.Select("/osis:osis/osis:osisText", xmlns);

You can read the file to a string, replace the namespace in memory, and then load it using a string stream:
string s;
using(var reader = File.OpenText("osis.xml"))
{
s = reader.ReadToEnd();
}
s = s.Replace("xmlns=\"http://www.bibletechnologies.net/2003/OSIS/namespace\"", "");
Stream stream = new MemoryStream(Encoding.ASCII.GetBytes(s));
XPathDocument document = new XPathDocument("stream");
// Rest of the code

XML reading from web and displaying content

I'm reading a file like from the web:
<?xml version='1.0' encoding='UTF-8'?>
<eveapi version="2">
<currentTime>2011-07-30 16:08:53</currentTime>
<result>
<rowset name="characters" key="characterID" columns="name,characterID,corporationName,corporationID">
<row name="Conqrad Echerie" characterID="91048359" corporationName="Federal Navy Academy" corporationID="1000168" />
</rowset>
</result>
<cachedUntil>2011-07-30 17:05:48</cachedUntil>
</eveapi>
im still new to XML and i see there are many ways to read XML data, is there a certain way im going to want to do this? what i want to do is load all the data into a StreamReader? and then use get; set; to pull the data later?

If you want object-based access, put the example xml in a file and run
xsd.exe my.xml
xsd.exe my.xsd /classes
this will create my.cs which is an object model similar to the xml that you can use with XmlSerializer:
var ser = new XmlSerializer(typeof(eveapi));
var obj = (eveapi)ser.Deserialize(source);

Use XmlReader Class or XmlTextReader Class
http://msdn.microsoft.com/en-us/library/aa720470(v=vs.71).aspx
http://msdn.microsoft.com/en-us/library/system.xml.xmltextreader(v=vs.71).aspx

If you need to use the data in the easy way, especially when you're new to XML, use XmlDocument.
To load the document:
using System.Xml;
using System.IO;
public class someclass {
void somemethod () {
//Initiate the XmlDocument object
XmlDocument xdoc;
//To load from file
xdoc.Load("SomeFolder\\SomeFile.xml");
//Or to load from XmlTextReader, from a file for example
FileStream fs = FileStream("SomeFolder\\SomeFile.xml", FileMode.Open, FileAccess.Read);
XmlTextReader reader = new XmlTextReader(fs);
xdoc.Load(reader);
//In fact, you can load the stream directly
xdoc.Load(fs);
//Or, you can load from a string
xdoc.LoadXml(#"<rootElement>
<element1>value1</element1>
<element2>value2</element2>
</rootElement>");
}
}
I personally find XmlDocument far easier to use for navigating an Xml file.
To use it efficiently, you need to learn XPath. For example, to get the name of the first row:
string name = xdoc.SelectSingleNode("/eveapi/result/rowset/row").Attribute["name"].InnerText;
or even more XPath:
string name = xdoc.SelectSingleNode("/eveapi/result/rowset/row/#name").InnerText;
you can even filter:
XmlNodeList elems = xdoc.SelectNodes("//*[#name=\"characters\"]")
gives you the rowset element.
But that's off topic.

determine if xml file contains data - c#

How do i know if my XML file has data besides the name space info:
Some of the files contain this:
<?xml version="1.0" encoding="UTF-8"?>
And if i encounter such a file, i want to place the file in an error directory

You could use the XmlReader to avoid the overhead of XmlDocument. In your case, you will receive an exception because the root element is missing.
string xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
using (StringReader strReader = new StringReader(xml))
{
//You can replace the StringReader object with the path of your xml file.
//In that case, do not forget to remove the "using" lines above.
using (XmlReader reader = XmlReader.Create(strReader))
{
try
{
while (reader.Read())
{
}
}
catch (XmlException ex)
{
//Catch xml exception
//in your case: root element is missing
}
}
}
You can add a condition in the while(reader.Read()) loop after you checked the first nodes to avoid to read the entire xml file since you just want to check if the root element is missing.

I think the only way is to catch an exception when you try and load it, like this:
try
{
System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
doc.Load(Server.MapPath("XMLFile.xml"));
}
catch (System.Xml.XmlException xmlEx)
{
if (xmlEx.Message.Contains("Root element is missing"))
{
// Xml file is empty
}
}
Yes, there is some overhead, but you should be performing sanity checks like this anyway. You should never trust input and the only way to reliably verify it is XML is to treat it like XML and see what .NET says about it!

XmlDocument xDoc = new XmlDocument();
if (xDoc.ChildNodes.Count == 0)
{ // xml document is empty }
if (xDoc.ChildNodes.Count == 1)
{ // in xml document is only declaration node. (if you are shure that declaration is allways at the begining }
if (xDoc.ChildNodes.Count > 1)
{ // there is declaration + n nodes (usually this count is 2; declaration + root node) }

Haven't tried this...but should work.
try
{
XmlDocument doc = new XmlDocument();
doc.Load("test.xml");
}
catch (XmlException exc)
{
//invalid file
}
EDIT: Based on feedback comments
For large XML documents see Thomas's answer. This approach can have performance issues.
But, if it is a valid xml and the program wants to process it then this approach seems better.

If you aren't worried about validity, just check to see if there is anything after the first ?>. I'm not entirely sure of the C# syntax (it's been too long since I used it), but read the file, look for the first instance of ?>, and see if there is anything after that index.
However, if you want to use the XML later or you want to process the XML later, you should consider PK's answer and load the XML into an XmlDocument object. But if you have large XML documents that you don't need to process, then a solution more like mine, reading the file as text, might have less overhead.

You could check if the xml document has a node (the root node) and check it that node has inner text or other children.

As long as you aren't concerned with the validity of the XML document, and only want to ensure that it has a tag other than the declaration, you could use simple text processing:
var regEx = new RegEx("<[A-Za-z]");
bool foundTags = false;
string curLine = "";
using (var reader = new StreamReader(fileName)) {
while (!reader.EndOfStream) {
curLine = reader.ReadLine();
if (regEx.Match(curLine)) {
foundTags = true;
break;
}
}
}
if (!foundTags) {
// file is bad, copy.
}
Keep in mind that there's a million other reasons that the file may be invalid, and the code above would validate a file consisting only of "<a". If your intent is to validate that the XML document is capable of being read, you should use the XmlDocument approach.