c# read attribute value

Question

ich have a xml file with the following structure:

<layer1 name="this is layer1">
  <messages>
    <message name ="com_request">0</message>
    <message name="send">1</message>
    <message name="request">2</message>
  </messages>
</layer1>

I try to collect all the message names in one indexer using the code:

SampleCollection<string> paramCollection = new SampleCollection<string>();

string pathxml = @"C:\myXML.xml";
int j=0;

XmlTextReader xmlin = new XmlTextReader(pathxml);
XmlDocument xmldoc = new XmlDocument();
XmlNode node = xmldoc.ReadNode(xmlin);

foreach (XmlNode item in node.ChildNodes)
{
   paramCollection[j] = item.Attributes["message name"].Value;
   Console.WriteLine(paramCollection[j]);
   j++;
}

However it doesn't work. Please help.

Can you be more specific with the error?

Paolo
– Paolo

2011-02-28 14:21:32 +00:00
Commented Feb 28, 2011 at 14:21 — Paolo
– Paolo, Commented Feb 28, 2011 at 14:21

Adam Robinson · Accepted Answer · 2011-02-28 14:23:59Z

3

The name of your attribute is name, not message name (message is the name of the node).

If you can describe more clearly what you're trying to do, I (or someone else) can provide a more specific solution.

answered Feb 28, 2011 at 14:23

Adam Robinson

186k36 gold badges294 silver badges351 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

BrokenGlass · Accepted Answer · 2011-02-28 14:28:49Z

1

In addition to what others have mentioned (attribute name is wrong), also your node points to layers1, who only has the direct child messages, so there are no message nodes in your child collection. The same thing in LINQ is trivial - switch if you can:

XDocument doc = XDocument.Load(@"test.xml");
foreach (var item in doc.Descendants("message"))
{
    Console.WriteLine(item.Attribute("name").Value);
}

answered Feb 28, 2011 at 14:28

BrokenGlass

161k28 gold badges297 silver badges339 bronze badges

2 Comments

JohnMunich Over a year ago

although i add using system.xml.linq.xdocument, the xdocument is underlined with red squiggle.

BrokenGlass Over a year ago

@JohnMunich: you should only need using System.Xml.Linq; for this to work

Steven Ryssaert · Accepted Answer · 2011-02-28 14:25:04Z

1

The attribute name is not message name, it is name

foreach (XmlNode item in node.ChildNodes)
{
   paramCollection[j] = item.Attributes["name"].Value;
   Console.WriteLine(paramCollection[j]);
   j++;
}

answered Feb 28, 2011 at 14:25

Steven Ryssaert

1,97715 silver badges28 bronze badges

Comments

marc_s · Accepted Answer · 2011-02-28 14:26:13Z

1

Try this:

XmlDocument xmldoc = new XmlDocument();

XmlNodeList list = xmldoc.SelectNodes("/layer1/messages/message");
List<string> messageNames = new List<string>();

foreach (XmlNode node in list)
{
   messageNames.Add(node.Attributes["name"].Value);    
}

This should extract all <message> nodes using XPath, and then grab their @name attribute into a list of strings.

answered Feb 28, 2011 at 14:26

marc_s

760k186 gold badges1.4k silver badges1.5k bronze badges

1 Comment

JohnMunich Over a year ago

could you give me any example about xpath?

Andy · Accepted Answer · 2011-02-28 14:27:21Z

1

Your node selection is wrong. Its needs to be more like:

string pathxml = @"C:\myXML.xml";
int j=0;

XmlTextReader xmlin = new XmlTextReader(pathxml);
XmlDocument xmldoc = new XmlDocument();
XmlNode node = xmldoc.ReadNode(xmlin);

foreach (XmlNode item in xmldoc.SelectNodes("layer1/messages/message"))
{
    paramCollection[j] = item.Attributes["name"].Value;
    Console.WriteLine(paramCollection[j]);
    j++;
}

So you get a collection of message nodes for the foreach to iterate over. Then the attribute is simple referenced as 'name'

answered Feb 28, 2011 at 14:27

Andy

7591 gold badge9 silver badges19 bronze badges

3 Comments

JohnMunich Over a year ago

its strange, it still doesn't work. Because of the comments:<?xml version="1.0" encoding="utf-8" standalone="yes" ?>

Andy Over a year ago

Can I see an example of the whole file please?

Andy Over a year ago

I have just spotted an issue with my code adjustment. Change xmldoc.SelectNodes("layer1/messages/message") to node.SelectNodes("messages/message")

Saeed Amiri · Accepted Answer · 2011-02-28 14:36:59Z

0

If you are using Linq to XML

var doc = XDocument.Load(@"d:\temp\myXml.xml");
var msgnames = from q in doc.Descendants("message")
               select q.Attribute("name").Value; 

foreach(string item in msgnames)
{
    Console.WriteLine(item);
}

edited Feb 28, 2011 at 14:36

Saeed Amiri

22.6k5 gold badges49 silver badges86 bronze badges

answered Feb 28, 2011 at 14:33

Murat Kazanova

3491 gold badge3 silver badges13 bronze badges

Comments

Dan Abramov · Accepted Answer · 2011-02-28 16:00:56Z

0

Firstly, as other have pointed out, your attribute is called name.

As for your task to collect some values in XML tree, you could have used XPath language to query the document. This would enable you to avoid writing boilerplate code that traverses the tree, as well as easily adapt to XML structure changes:

var doc = new XmlDocument ();
doc.LoadXml (xs);

var attrs = doc.SelectNodes ("/layer1/messages/message/@name");
var values = attrs.Cast<XmlAttribute> ()
    .Select (a => a.Value);

However, since I already used LINQ to cast nodes into attribute instances, it makes sense to use LINQ to XML instead, which was designed for querying XML from C# code:

var doc = XDocument.Parse (xs);
var values = from msg in doc.Descendants ("message")
             select msg.Attribute ("name").Value;

Console.WriteLine (values);

Both of these options are good and depend on what framework you plan to use for working with XML, System.Xml or LINQ to XML. For new code, I suggest using LINQ.

In both cases, you need a simple foreach loop to enumerate values:

foreach (string value in values)
    Console.WriteLine (value);

edited Feb 28, 2011 at 16:00

answered Feb 28, 2011 at 14:41

Dan Abramov

269k87 gold badges417 silver badges523 bronze badges

2 Comments

JohnMunich Over a year ago

how to retrieve the value in the values?

Dan Abramov Over a year ago

Sorry, I don't understand what you mean. values in both cases is of type IEnumerable<string>, meaning you can go through them in a foreach loop: foreach (string value in values). If you need a List<string> or string [] array, call ToList or ToArray on values.

Collectives™ on Stack Overflow

c# read attribute value

7 Answers 7

Comments

2 Comments

Comments

1 Comment

3 Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

Comments

2 Comments

Comments

1 Comment

3 Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related