I'm writing a file reader using the XmlReader in a Silverlight project. However, I'm getting some errors (specifically around the XmlReader.ReadStartElement method) and it's causing me to believe that I've misunderstood how to use it somewhere along the way.
Basically, here is a sample of the format of the Xml I am using:
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<root>
<EmptyElement />
<NonEmptyElement Name="NonEmptyElement">
<SubElement Name="SubElement" />
</NonEmptyElement>
</root>
And here is a sample of some code used in the same way as how I am using it:
public void ReadData(XmlReader reader)
{
// Move to root element
reader.ReadStartElement("root");
// Move to the empty element
reader.ReadStartElement("EmptyElement");
// Read any children
while(reader.ReadToNextSibling("SubEmptyElement"))
{
// ...
}
// Read the end of the empty element
reader.ReadEndElement();
// Move to the non empty element
reader.ReadStartElement("NonEmptyElement"); // NOTE: This is where I get the error.
// ...
}
So, essentially, I am simply trying to read each element and any contained children. The error I get at the highlighted point is as follows:
Error Description
[Xml_InvalidNodeType]
Arguments: None,10,8
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.51204.0&File=System.Xml.dll&Key=Xml_InvalidNodeType
Error Stack Trace
at System.Xml.XmlReader.ReadStartElement(String name)
at ----------------
Any advice or direction on this would be greatly appreciated.
EDIT
Since this reader needs to be fairly generic, it can be assumed that the Xml may contain elements that are children of the EmptyElement. As such, the attempt at reading any SubEmptyElements should be valid.
<SubElement/> is not a sibling of <EmptyElement>, so <NonEmptyElement> is going to get skipped entirely, and your call to ReadEndElement() will read the end element </root>. When you try to subsequently read "NonEmptyElement", there are no elements left, and you'll get an XmlException: {"'None' is an invalid XmlNodeType. Line 8, position 1."}
Note also that since <EmptyElement/> is empty, when you ReadStartElement("EmptyElement"), you'll read the whole element, and you won't need to use ReadEndElement().
I'd also recommend that you configure your reader settings to IgnoreWhitespace (if you're not already doing so), to avoid any complications introduced by reading (insignificant) whitespace text nodes when you aren't expecting them.
Try moving the Read of NonEmptyElement up:
public static void ReadData(XmlReader reader)
{
reader.ReadStartElement("root");
reader.ReadStartElement("EmptyElement");
reader.ReadStartElement("NonEmptyElement");
while (reader.ReadToNextSibling("SubEmptyElement"))
{
// ...
}
reader.ReadEndElement(/* NonEmptyElement */);
reader.ReadEndElement(/* root */);
// ...
}
If you just want to skip anything in <EmptyElement>, regardless of whether or not its actually empty, use ReadToFollowing:
public static void ReadData(XmlReader reader)
{
reader.ReadStartElement("root");
reader.ReadToFollowing("NonEmptyElement");
Console.WriteLine(reader.GetAttribute("Name"));
reader.ReadStartElement("NonEmptyElement");
Console.WriteLine(reader.GetAttribute("Name"));
while (reader.ReadToNextSibling("SubEmptyElement"))
{
// ...
}
reader.ReadEndElement(/* NonEmptyElement */);
reader.ReadEndElement(/* root */);
// ...
}
Update: Here's a fuller example with a clearer data model. Maybe this is closer to what you're asking for.
XMLFile1.xml:
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<root>
<Person Type="Homeless"/>
<Person Type="Developer">
<Home Type="Apartment" />
</Person>
<Person Type="Banker">
<Home Type="Apartment"/>
<Home Type="Detached"/>
<Home Type="Mansion">
<PoolHouse/>
</Home>
</Person>
</root>
Program.cs:
using System;
using System.Xml;
namespace ConsoleApplication6
{
internal class Program
{
public static void ReadData(XmlReader reader)
{
reader.ReadStartElement("root");
while (reader.IsStartElement("Person"))
{
ReadPerson(reader);
}
reader.ReadEndElement( /* root */);
}
public static void ReadPerson(XmlReader reader)
{
Console.WriteLine(reader.GetAttribute("Type"));
bool isEmpty = reader.IsEmptyElement;
reader.ReadStartElement("Person");
while (reader.IsStartElement("Home"))
{
ReadHome(reader);
}
if (!isEmpty)
{
reader.ReadEndElement( /* Person */);
}
}
public static void ReadHome(XmlReader reader)
{
Console.WriteLine("\t" + reader.GetAttribute("Type"));
bool isEmpty = reader.IsEmptyElement;
reader.ReadStartElement("Home");
if (!isEmpty)
{
reader.Skip();
reader.ReadEndElement( /* Home */);
}
}
private static void Main(string[] args)
{
var settings = new XmlReaderSettings { IgnoreWhitespace = true };
using (var xr = XmlReader.Create("XMLFile1.xml", settings))
{
ReadData(xr);
}
Console.ReadKey();
}
}
}
Related
I have written an Xml file using XmlWriter.
Here is the code:
public void WriteXml(XmlWriter writer)
{
writer.WriteStartElement("element1");
writer.WriteAttributeString("attrs1", Attrs1);
writer.WriteAttributeString("attrs2", Attrs2);
if (!string.IsNullOrWhiteSpace("element2"))
{
writer.WriteStartElement("element2");
writer.WriteCData(Element2);
writer.WriteEndElement();
}
if (!string.IsNullOrWhiteSpace("element3"))
{
writer.WriteStartElement("element3");
writer.WriteCData(Element3);
writer.WriteEndElement();
}
Element4.WriteXml(writer);
Element5.WriteXml(writer);
writer.WriteEndElement();
}
As you can see, element4 calls a method named "WriteXml()". Here is that method:
public void WriteXml(XmlWriter writer)
{
if (m_PropertyValueList.Count > 0)
{
writer.WriteStartElement("element4");
foreach (var p in m_PropertyValueList)
{
if (p.CurrentValue != null)
{
writer.WriteStartElement("property");
writer.WriteAttributeString("name", p.PropertyName);
writer.WriteAttributeString("value", p.CurrentValue.ToString());
writer.WriteEndElement();
}
}
writer.WriteEndElement();
}
}
Notice that it checks for p.CurrentValue != null. If it is null then this element should be written as an empty element. In this case, p.CurrentValue is null so I do want an empty element. You will see in the Xml output below that is writing this element as . To me it looks like it is properly writing an empty element, PLEASE CORRECT ME IF I'M WRONG HERE.
The Xml file output looks like this:
<?xml version="1.0" encoding="UTF-8"?>
-<element>
-<element 1 attrs1="Some Info" attrs2="More Info">
-<element2>
+<![CDATA[]]>
</element2>
-<element3>
-<![CDATA[ ]]>
</element3>
<element4/>
</element1>
</element>
Then I create a method for reading the Xml file back in. This is where it breaks. It does just fine reading element, element1, element2 and element3. However, when it gets to element4, I start having issues. I will explain below.
Here is the XmlReader method:
public void ReadXml(XmlReader reader)
{
if (reader.IsStartElement("element1"))
{
//
// Get the values of all the <element1> attributes
//
Attrs1= reader.GetAttribute("attrs1");
Attrs2 = reader.GetAttribute("attrs2");
//
// Read past <element1>
//
reader.Read();
while (true)
{
if (reader.IsStartElement("element2"))
{
Description = reader.ReadElementContentAsString();
}
else if (reader.IsStartElement("element3"))
{
Source = reader.ReadElementContentAsString();
}
else if (reader.IsStartElement("element4")) && (!reader.IsEmptyElement))
{
Element4.ReadXml(reader);
}
else if ((reader.IsStartElement("element5")) && (!reader.IsEmptyElement))
{
Element5.ReadXml(reader);
}
else
{
reader.MoveToContent();
reader.ReadEndElement();
break;
}
}
}
else
{
throw new XmlException("Expected <element1> element was not present");
}
}
Notice that if element4 IsStartElement and if it's not an empty element it will call Element4.ReadXml(). Here is that method:
public void ReadXml(XmlReader reader)
{
if ((reader.IsStartElement("element4")) && (!reader.IsEmptyElement))
{
reader.Read();
while (reader.IsStartElement("property"))
{
string propertyName = reader.GetAttribute("name");
string propertyValue = reader.GetAttribute("value");
SetValue(propertyName, propertyValue);
reader.Read();
}
//
// Read </element4>
//
reader.MoveToContent();
reader.ReadEndElement();
}
}
But since element4 IS empty this method never gets called. So it will continue to the else{} statement and break when it gets to reader.ReadEndElement(); There error message I get is:
"Message: TestMethod myTestMethodName threw exception: System.Xml.XmlException 'Element' is an invalid XmlNodeType. Line 8, position 6."
So my questions are:
Is this because the element is empty? If so, how do I close or read past an empty element?
Where I am reading element4 if it's start element and if it's not empty....If I remove (!reader.IsEmptyElement) I get an infinite loop. It continues to call Element4.ReadXml(reader). Why is this?
How to I fix and continue past this so that I can read the rest of the elements.
Where I read my elements from my xml file I needed to add another else if condition to handle if the element is start element and if the element IS empty. I was only checking if it wasn't empty. So it didn't know how to handle it being empty. Then when those conditions were met I simply had to do reader.Read() to tell the app to read the element as is <element4/>.
Here is what it looks like:
else if (reader.IsStartElement("element4")) && (reader.IsEmptyElement))
{
reader.Read();
}
XML :
<InformationTuples>
<InformationTuple>
<Name>documentClass</Name>
<value format="" valueset="{rechnung}" originalValue="Rechnung" start="0" end="0" LD="0" doc="C:\b4enviam-service-test\inputDir\031a0933-2616-4d8e-8a79-56746ae0e160/Invoice_51029062.pdf">Rechnung</value>
<EntityType>Class</EntityType>
<state>New </state>
<need>Mandatory </need>
<extractionmethod>
</extractionmethod>
<weight>1</weight>
<precondition type="optional">All</precondition>
</InformationTuple>
<InformationTuple>
<Name>SAPNr.</Name>
<value format="" valueset="" originalValue="4352020616" start="0" end="0" LD="0" doc="C:\b4enviam-service-test\inputDir\031a0933-2616-4d8e-8a79-56746ae0e160/Invoice_51029062.pdf">4352020616</value>
<EntityType>KB.GTInovice</EntityType>
<state>New </state>
<need>Mandatory </need>
<extractionmethod>
</extractionmethod>
<weight>1</weight>
<precondition type="optional">all</precondition>
</InformationTuple>
<InformationTuple>
<Name>GT-Invoice</Name>
<value format="" valueset="" originalValue="" start="0" end="0" LD="0" doc="">
</value>
<EntityType>KB.GTInovice</EntityType>
<state>New </state>
<need>Mandatory </need>
<extractionmethod>
</extractionmethod>
<weight>1</weight>
<precondition type="optional">all</precondition>
</InformationTuple>
</InformationTuples>
C#
reader.ReadToFollowing("InformationTuple");
reader2.ReadToFollowing("InformationTuple");
do
{
subtree = reader2.ReadSubtree();
subtree.ReadToFollowing("Name");
Debug.WriteLine(subtree.ReadElementContentAsString());
reader2.ReadToNextSibling("InfromationTuple");
} while (reader.ReadToNextSibling("InformationTuple"))
I'm trying for a while now to extract data from multiple childs in XML using c# but didn't successful. I have tried multiple code snippets but unable to extract data.
Like i have to extract the data given in three information tuples, but functions given in the XMLreader not working properly reader pointer break after single loop iteration (unable to move to second InformationTuple), even i have tried two different reader pointer but its now giving exception.
Need little help ,
Thanks
You can read the first <Name> element inside each <InformationTuple> as follows. Introduce the following extension methods:
public static partial class XmlReaderExtensions
{
public static IEnumerable<string> ReadAllElementContentsAsString(this XmlReader reader, string localName, string namespaceURI)
{
while (reader.ReadToFollowing(localName, namespaceURI))
yield return reader.ReadElementContentAsString();
}
public static IEnumerable<XmlReader> ReadAllSubtrees(this XmlReader reader, string localName, string namespaceURI)
{
while (reader.ReadToFollowing(localName, namespaceURI))
using (var subReader = reader.ReadSubtree())
yield return subReader;
}
}
And then do:
foreach (var name in reader.ReadAllSubtrees("InformationTuple", "")
.Select(r => r.ReadAllElementContentsAsString("Name", "").First()))
{
// Process the name somehow
Debug.WriteLine(name);
}
If you want to only read the first <Name> element of each <InformationTuple> element inside each <InformationTuples> container, you can restrict the scope of the search by composing calls to ReadAllSubtrees() using SelectMany():
foreach (var name in reader.ReadAllSubtrees("InformationTuples", "")
.SelectMany(r => r.ReadAllSubtrees("InformationTuple", ""))
.Select(r => r.ReadAllElementContentsAsString("Name", "").First()))
{
// Process the name somehow
Debug.WriteLine(name);
}
Some notes:
You don't close (or dispose) your ReadSubtree() subtree reader when you are done with it. From the docs:
You should not perform any operations on the original reader until the new reader has been closed. This action is not supported and can result in unpredictable behavior.
Thus you must close or dispose this nested reader before advancing the outer reader.
You have too many calls to reader.ReadToFollowing("InformationTuple"); at the beginning. Perhaps you meant to do reader.ReadToFollowing("InformationTuples");?
To ensure there is one and only one <Name> element for each <InformationTuple> replace First() with .Single().
If there might be multiple <Name> nodes for each <InformationTuple> and you want to read all of them, do:
foreach (var name in reader.ReadAllSubtrees("InformationTuple", "")
.SelectMany(r => r.ReadAllElementContentsAsString("Name", "")))
{
// Process the name somehow
Demo fiddle here.
The code below I used a lot and will not create any errors.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;
namespace ConsoleApplication1
{
class Program
{
const string FILENAME = #"c:\temp\test.xml";
static void Main(string[] args)
{
XmlReader reader = XmlReader.Create(FILENAME);
while (!reader.EOF)
{
if (reader.Name != "InformationTuple")
{
reader.ReadToFollowing("InformationTuple");
}
if (!reader.EOF)
{
XElement subtree = (XElement)XElement.ReadFrom(reader);
Info.info.Add(new Info() { state = (string)subtree.Element("state"), weight = (int)subtree.Element("weight") });
}
}
}
}
public class Info
{
public static List<Info> info = new List<Info>();
public string state { get; set; }
public int weight { get; set; }
}
}
Thank you very much for reading my question.
the bottom is the sample of my xml file.please refer that.
i did some xml files before, but by "CMarkXml". "IntoElement, OutofElement", is very clear.
but when C#...i was lost..
1: how to read & write my xml file without using the tag name. i see some articles about operation on xml file by c#, but all assumed that known the tag name.
2: if without tag name, it is very difficult or not recommend. then how to read & write my xml file by XmlDocument? (sorry, but no Ling please, i am very faint with that...).
3: my idear is, for the xml file, get out some section, we still could parse the section by xmldocument.
4: for the write/modify the xml file, of course, should contain delete some section, delete some "leaf", change the attributes...
Thank you very much for reading the long question, and any help i will very appreciate. If you have a good sample code but not continent paste them here, could you send it to "erlvde#gmail.com"?
<root>
<a>i belong to a</a>
<b>
<bb>
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
</bb>
<bb>
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
<bb>
....(other <bb>)
</b>
</root>
Read your xml into XmlDocument:
var xmlDocument = new XmlDocument();
xmlDocument.LoadXml("XML HERE");
Access child nodes:
xmlDocument.ChildNodes[1]
But it's also true that it's very error prone
You can also check if you have child nodes at all:
xmlDocument.HasChildNodes
And get number of child nodes:
xmlDocument.ChildNodes.Count
It looks to me like your elements names contain identifiers. If that is the case, and you have control over the XML schema, I would highly recommend changing your XML to contain elements and/or attributes indicating your identifiers and then use the built in XmlSerializer class for serializing to and from XML. It has many modifiers available, such as XmlElement and XmlAttribute among many others, for formatting the output.
Here is a tutorial to get you started.
If possible, change your XML to something like following which would make it far simpler to manipulate...again if changing the schema is a possibility.
<root>
<a>i belong to a</a>
<b>
<bb id="1">
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
</bb>
<bb id="2">
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
<bb>
</b>
</root>
Edit this edit reflects the changes you made to your XML
Here is a simple console application which will serialize an object to an XML file and then rehydrate it.
Expected XML
<?xml version="1.0" encoding="utf-8"?>
<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<a>i belong to a</a>
<b>
<bb>
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
</bb>
<bb>
<bb>1</bb>
<bb>2</bb>
<bb>3</bb>
<bb>4</bb>
<bb>5</bb>
</bb>
</b>
</root>
Simple Console Application Demonstration
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Serialization;
using System.IO;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
var items = new root
{
a = "i belong to a",
b = new List<bb>
{
new bb
{
bbClassProperty = new List<int>
{
1,
2,
3,
4,
5
}
},
new bb
{
bbClassProperty= new List<int>
{
1,
2,
3,
4,
5
}
}
}
};
XmlSerializer serializer = new XmlSerializer(typeof(root));
using (var textWriter = new StreamWriter(#"C:\root.xml"))
{
serializer.Serialize(textWriter, items);
textWriter.Close();
}
using (var stream = new StreamReader(#"C:\root.xml"))
{
var yourObject = serializer.Deserialize(stream);
}
Console.Read();
}
}
#region [Classes]
public class root
{
public string a { get; set; }
public List<bb> b { get; set; }
}
public class bb
{
[XmlElement("bb")]
public List<int> bbClassProperty { get; set; }
}
#endregion
}
Look into the ChildNodes (and similar) properties and methods on your XmlElement object. These will let you iterate over the children of a node and you can then ask that node for its name.
If you have a XmlNode object, you can use XMLNode.FirstChild to get the child, if it has any. You can also use XMLNode.NextSibling to get the next Node of the same parent node.
Why can't you use the names of the nodes? It's the easiest and most common way. Especially if you use XPath or similar.
XPath is also the answer to your second question.
U can use the class XML reader, a simple example is given here.
using System;
using System.Xml;
class Program
{
static void Main()
{
// Create an XML reader for this file.
using (XmlReader reader = XmlReader.Create("perls.xml"))
{
while (reader.Read())
{
// Only detect start elements.
if (reader.IsStartElement())
{
// Get element name and switch on it.
switch (reader.Name)
{
case "perls":
// Detect this element.
Console.WriteLine("Start <perls> element.");
break;
case "article":
// Detect this article element.
Console.WriteLine("Start <article> element.");
// Search for the attribute name on this current node.
string attribute = reader["name"];
if (attribute != null)
{
Console.WriteLine(" Has attribute name: " + attribute);
}
// Next read will contain text.
if (reader.Read())
{
Console.WriteLine(" Text node: " + reader.Value.Trim());
}
break;
}
}
}
}
}
}
The input file text is:
<?xml version="1.0" encoding="utf-8" ?>
<perls>
<article name="backgroundworker">
Example text.
</article>
<article name="threadpool">
More text.
</article>
<article></article>
<article>Final text.</article>
</perls>
Output
Start element.
Start element.
Has attribute name: backgroundworker
Text node: Example text.
Start element.
Has attribute name: threadpool
Text node: More text.
Start element.
Text node:
Start element.
Text node: Final text.enter code here
You can use the following code to if the file does not contain the headers, in the example above.
XmlReaderSettings settings = new XmlReaderSettings();
settings.ConformanceLevel = ConformanceLevel.Fragment;
reader = XmlReader.Create(filePath, settings)
Would something like this help?
void Iterate(XmlNode parent) {
//do something with
//parent.Name
//parent.Value
//parent.Attributes
foreach(XmlNode child in parent.ChildNodes) {
Iterate(child);
}
}
XmlDocument document = new XmlDocument();
document.Load(filename);
XmlNode parent = document.DocumentElement;
Iterate(parent);
You could also store it like that (sorry for any syntactical error, didn't run it)
public class Document {
public Element DocumentElement { set; get; }
private void Load(string fileName) {
XmlDocument document = new XmlDocument();
document.Load(fileName);
DocumentElement = new Element(this, null);
DocumentElement.Load(document.DocumentElement);
}
}
public class Element {
public string Name { set; get; }
public string Value { set; get; }
//other attributes
private Document document = null;
private Element parent = null;
public Element Parent { get { return parent; } }
public List<Element> Children { set; get; }
private int order = 0;
public Element(Document document, Element parent) {
Name = "";
Value = "";
Children = new List<LayoutElement>();
this.document = document;
this.parent = parent;
order = parent != null ? parent.Children.Count + 1 : 1;
}
private Element GetSibling(bool left) {
if(parent == null) return null;
int add = left ? -1 : +1;
Element sibling = parent.Children.Find(child => child.order == order + add);
return sibling;
}
public Element GetLeftSibling() {
return GetSibling(true);
}
public Element GetRightSibling() {
return GetSibling(false);
}
public void Load(XmlNode node) {
Name = node.Name;
Value = node.Value;
//other attributes
foreach(XmlNode nodeChild in node.Children) {
Element child = new Element(document, this);
child.Load(nodeChild);
Children.Add(child);
}
}
}
Document document = new Document();
document.Load(fileName);
For changing/deleting right now you could iterate the tree and find elements by name, but since name is not unique, you would affect many elements at once. You could add an unique id in every tag like
<bb id="bb1"/>
Then read it in Load function like
id = ((XmlElement)node).GetAttribute("id");
and use this id to iterate through the tree. Sorry I don't have time right now to provide something more detailed.
I'm getting the exception that NodeType "None" is not supported when trying to run the following code.
public int ObjectContentI(string XmlPath)
{
XmlNodeReader xnr = new XmlNodeReader(this.xmlr.SelectSingleNode(XmlPath));
return xnr.ReadElementContentAsInt();
}
this.xmlr is a XmlDocument with a document successfully loaded in it. XmlPath contains a valid XPath url.
How do i set the NodeType (xnr.NodeType is readonly) or am I doing something else wrong?
Part of my XML:
<?xml version="1.0" encoding="utf-8" ?>
<ship weapons="0">
<cost>
<metal>250</metal>
<crystal>100</crystal>
</cost>
<health>
<shields>750</shields>
<sregene>10</sregene>
<hitpoints>1000</hitpoints>
<oxygen cps="2">25000</oxygen>
</health>
My XPath: "/ship/health/shields/text()"
Well, your approach is correct but not completely.
Let's suppose
XmlNode n = myXMLDoc.SelectSingleNode("/ship/health/shields/");
n.InnerXML OR n.InnerText should give you what you need.
Though conqenator provided you with code that fixed your problem following is reasoning why it didn't work in the first place:
If you don't call the Read method on a XmlNodeReader or any of the classes that derive from XmlReader, you will always get a XmlNodeType.None NodeType, which is the reason for the error. To fix the code you provided and to get an int back this is what the code needs to look like:
public int ObjectContentI(string XmlPath)
{
int result;
using(XmlNodeReader xnr = new XmlNodeReader(this.xmlr.SelectSingleNode(XmlPath))){
while(xnr.Read()){
result = xnr.ReadElementContentAsInt();
}
}
return result;
}
Note that the XPath to get this wroking needs to change to /ship/health/shields since ReadElementContentAsInt() returns the content of the element and won't work on a Text Node, which what you get when using /ship/health/shields/text().
Notice that I have also wrapped the XmlNodeReader in a using block, which will dispose of the XmlNodeReader once you are done with it to free up resources.
I am storing logs in an xml file...
In a traditional straight text format approach, you would typically just have a openFile... then writeLine method...
How is it possible to add a new entry into the xml document structure, like you would just with the text file approach?
use an XmlWriter.
example code:
public class Quote
{
public string symbol;
public double price;
public double change;
public int volume;
}
public void Run()
{
Quote q = new Quote
{
symbol = "fff",
price = 19.86,
change = 1.23,
volume = 190393,
};
WriteDocument(q);
}
public void WriteDocument(Quote q)
{
var settings = new System.Xml.XmlWriterSettings
{
OmitXmlDeclaration = true,
Indent= true
};
using (XmlWriter writer = XmlWriter.Create(Console.Out, settings))
{
writer.WriteStartElement("Stock");
writer.WriteAttributeString("Symbol", q.symbol);
writer.WriteElementString("Price", XmlConvert.ToString(q.price));
writer.WriteElementString("Change", XmlConvert.ToString(q.change));
writer.WriteElementString("Volume", XmlConvert.ToString(q.volume));
writer.WriteEndElement();
}
}
example output:
<Stock Symbol="fff">
<Price>19.86</Price>
<Change>1.23</Change>
<Volume>190393</Volume>
</Stock>
see
Writing with an XmlWriter
for more info.
One of the problems with writing a log file in XML format is that you can't just append lines to the end of the file, because the last line has to have a closing root element (for the XML to be valid)
This blog post by Filip De Vos demonstrates quite a good solution to this:
High Performance writing to XML Log files (edit: link now dead so removed)
Basically, you have two XML files linked together using an XML-include thing:
Header file:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log [
<!ENTITY loglines SYSTEM "loglines.xml">
]>
<log>
&loglines;
</log>
Lines file (in this example, named loglines.xml):
<logline date="2007-07-01 13:56:04.313" text="start process" />
<logline date="2007-07-01 13:56:25.837" text="do something" />
<logline date="2007-07-01 13:56:25.853" text="the end" />
You can then append new lines to the 'lines file', but (most) XML parsers will be able to open the header file and read the lines correctly.
Filip notes that: This XML will not be parsed correctly by every XML parser on the planet. But all the parsers I have used do it correctly.
The big difference is the way you are thinking about your log data. In plain text files you are indeed just adding new lines. XML is a tree structure however, and you need to think about like such. What you are adding is probably another NODE, i.e.:
<log>
<time>12:30:03 PST</time>
<user>joe</user>
<action>login</action>
<log>
Because it is a tree what you need to ask is what parent are you adding this new node to. This is usually all defined in your DTD (Aka, how you are defining the structure of your data). Hopefully this is more helpful then just what library to use as once you understand this principle the interface of the library should make more sense.
Why reinvent the wheel? Use TraceSource Class (System.Diagnostics) with the XmlWriterTraceListener.
Sorry to post a answer for old thread. i developed the same long time ago. here i like to share my full code for logger saved log data in xml file date wise.
logger class code
using System.IO;
using System.Xml;
using System.Threading;
public class BBALogger
{
public enum MsgType
{
Error ,
Info
}
public static BBALogger Instance
{
get
{
if (_Instance == null)
{
lock (_SyncRoot)
{
if (_Instance == null)
_Instance = new BBALogger();
}
}
return _Instance;
}
}
private static BBALogger _Instance;
private static object _SyncRoot = new Object();
private static ReaderWriterLockSlim _readWriteLock = new ReaderWriterLockSlim();
private BBALogger()
{
LogFileName = DateTime.Now.ToString("dd-MM-yyyy");
LogFileExtension = ".xml";
LogPath= Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location) + "\\Log";
}
public StreamWriter Writer { get; set; }
public string LogPath { get; set; }
public string LogFileName { get; set; }
public string LogFileExtension { get; set; }
public string LogFile { get { return LogFileName + LogFileExtension; } }
public string LogFullPath { get { return Path.Combine(LogPath, LogFile); } }
public bool LogExists { get { return File.Exists(LogFullPath); } }
public void WriteToLog(String inLogMessage, MsgType msgtype)
{
_readWriteLock.EnterWriteLock();
try
{
LogFileName = DateTime.Now.ToString("dd-MM-yyyy");
if (!Directory.Exists(LogPath))
{
Directory.CreateDirectory(LogPath);
}
var settings = new System.Xml.XmlWriterSettings
{
OmitXmlDeclaration = true,
Indent = true
};
StringBuilder sbuilder = new StringBuilder();
using (StringWriter sw = new StringWriter(sbuilder))
{
using (XmlWriter w = XmlWriter.Create(sw, settings))
{
w.WriteStartElement("LogInfo");
w.WriteElementString("Time", DateTime.Now.ToString());
if (msgtype == MsgType.Error)
w.WriteElementString("Error", inLogMessage);
else if (msgtype == MsgType.Info)
w.WriteElementString("Info", inLogMessage);
w.WriteEndElement();
}
}
using (StreamWriter Writer = new StreamWriter(LogFullPath, true, Encoding.UTF8))
{
Writer.WriteLine(sbuilder.ToString());
}
}
catch (Exception ex)
{
}
finally
{
_readWriteLock.ExitWriteLock();
}
}
public static void Write(String inLogMessage, MsgType msgtype)
{
Instance.WriteToLog(inLogMessage, msgtype);
}
}
Calling or using this way
BBALogger.Write("pp1", BBALogger.MsgType.Error);
BBALogger.Write("pp2", BBALogger.MsgType.Error);
BBALogger.Write("pp3", BBALogger.MsgType.Info);
MessageBox.Show("done");
may my code help you and other :)
Without more information on what you are doing I can only offer some basic advice to try.
There is a method on most of the XML objects called "AppendChild". You can use this method to add the new node you create with the log comment in it. This node will appear at the end of the item list. You would use the parent element of where all the log nodes are as the object to call on.
Hope that helps.
XML needs a document element (Basically top level tag starting and ending the document).
This means a well formed XML document need have a beginning and end, which does not sound very suitable for logs, where the current "end" of the log is continously extended.
Unless you are writing batches of self contained logs where you write everything to be logged to one file in a short period of time, I'd consider something else than XML.
If you are writing a log of a work-unit done, or a log that doesn't need to be inspected until the whole thing has finished, you could use your approach though - simply openfile, write the log lines, close the file when the work unit is done.
For editing an xml file, you could also use LINQ. You can take a look on how here:
http://www.linqhelp.com/linq-tutorials/adding-to-xml-file-using-linq-and-c/