XmlTextReader - how find a particular node

[CodeRazor]

I am reading an xml file from a URL. I was originally doing this using the
XmlDocument class. But this was very slow. The XmlTextReader is meant to be
much quicker for forward only retrieval of data.

I need to somehow access a particular list of nodes. e.g. I want to loop
through all the nodes called <item></item>. How is this possible using
XmlTextReader?
I can see that you can get the .Value property of XmlTextReader. But I want
to be able to specify the node I want to look at.

e.g.

<Group>
<Items>
<Item>content here</Item>
<Item>some more content here</Item>
<Items>
<Activity></Activity>
<Location></Location>
</Group>

thanks.

CR

[Marc Gravell]

Re: XmlTextReader - how find a particular node

you can use ReadToFollowing ("Item") to jump to each Item - however, you need
to be careful, as the "intuitive" code might be (IIRC) wrong:

while(reader.Re adToFollowing(" Item")) {
string content = reader.ReadElem entContentAsStr ing();
// do something with content
}

The reason this is wrong is that ReadElementCont entAsString progresses
/past/ the [Item] element, so the next call to ReadToFollowing () might skip
the next row; you might be able-to do something with a sub-reader, else you
might need to check (after calling ReadElementCont entAsString) if you are on
an Item element; if you are, it is the *next* one, so read it; if you
aren't, then ReadToFollowing

Marc

"CodeRazor" <CodeRazor@disc ussions.microso ft.com> wrote in message
news:C1FA6EED-1E92-41BD-8F50-0B07182D27FA@mi crosoft.com...[color=blue]
>I am reading an xml file from a URL. I was originally doing this using the
> XmlDocument class. But this was very slow. The XmlTextReader is meant to
> be
> much quicker for forward only retrieval of data.
>
> I need to somehow access a particular list of nodes. e.g. I want to loop
> through all the nodes called <item></item>. How is this possible using
> XmlTextReader?
> I can see that you can get the .Value property of XmlTextReader. But I
> want
> to be able to specify the node I want to look at.
>
> e.g.
>
> <Group>
> <Items>
> <Item>content here</Item>
> <Item>some more content here</Item>
> <Items>
> <Activity></Activity>
> <Location></Location>
> </Group>
>
> thanks.
>
> CR[/color]

[Michael Nemtsev]

Re: XmlTextReader - how find a particular node

Hello CodeRazor,

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemxmlxmltextreaderclassnametopic.asp

use .Read() methods of XmlTextReader and then in switch (reader.NodeTyp e)
check the case XmlNodeType.Ele ment u want to find


C> I am reading an xml file from a URL. I was originally doing this
C> using the XmlDocument class. But this was very slow. The
C> XmlTextReader is meant to be much quicker for forward only retrieval
C> of data.
C>
C> I need to somehow access a particular list of nodes. e.g. I want to
C> loop
C> through all the nodes called <item></item>. How is this possible
C> using
C> XmlTextReader?
C> I can see that you can get the .Value property of XmlTextReader. But
C> I want
C> to be able to specify the node I want to look at.
C> e.g.
C>
C> <Group>
C> <Items>
C> <Item>content here</Item>
C> <Item>some more content here</Item>
C> <Items>
C> <Activity></Activity>
C> <Location></Location>
C> </Group>
C> thanks.
C>
C> CR
C>
---
WBR,
Michael Nemtsev :: blog: http://spaces.msn.com/laflour

"At times one remains faithful to a cause only because its opponents do not
cease to be insipid." (c) Friedrich Nietzsche

[Marc Gravell]

Re: XmlTextReader - how find a particular node

et voila (note your xml was malformed); also, generally (for large xml) I
wouldn't use a string and MemoryStream here unless I had to - but it was the
only 1-line way I could think of to initialise the reader. Loading directly
from the uri (or a file) would be an option, though...

Marc

using System;
using System.Xml;
using System.Text;
using System.IO;
namespace ReadSomeXml {
class Program {
static void Main(string[] args)
{
string xml = @"<Group>
<Items>
<Item>content here</Item>
<Item>some more content here</Item>
</Items>
<Activity></Activity>
<Location></Location>
</Group>";
using(XmlReader reader = XmlReader.Creat e(new
MemoryStream(En coding.UTF8.Get Bytes(xml)))) {

while(true) {
if(reader.NodeT ype == XmlNodeType.Ele ment && reader.Name
== "Item") {
string content =
reader.ReadElem entContentAsStr ing();
Console.WriteLi ne(content);
} else {
if(!reader.Read ToFollowing("It em")) break;
}
}
}
}
}
}
"Marc Gravell" <marc@nonesuch. com> wrote in message
news:eN47sAsRGH A.3192@TK2MSFTN GP09.phx.gbl...[color=blue]
> you can use ReadToFollowing ("Item") to jump to each Item - however, you
> need to be careful, as the "intuitive" code might be (IIRC) wrong:
>
> while(reader.Re adToFollowing(" Item")) {
> string content = reader.ReadElem entContentAsStr ing();
> // do something with content
> }
>
> The reason this is wrong is that ReadElementCont entAsString progresses
> /past/ the [Item] element, so the next call to ReadToFollowing () might
> skip the next row; you might be able-to do something with a sub-reader,
> else you might need to check (after calling ReadElementCont entAsString) if
> you are on an Item element; if you are, it is the *next* one, so read it;
> if you aren't, then ReadToFollowing
>
> Marc
>
> "CodeRazor" <CodeRazor@disc ussions.microso ft.com> wrote in message
> news:C1FA6EED-1E92-41BD-8F50-0B07182D27FA@mi crosoft.com...[color=green]
>>I am reading an xml file from a URL. I was originally doing this using
>>the
>> XmlDocument class. But this was very slow. The XmlTextReader is meant to
>> be
>> much quicker for forward only retrieval of data.
>>
>> I need to somehow access a particular list of nodes. e.g. I want to loop
>> through all the nodes called <item></item>. How is this possible using
>> XmlTextReader?
>> I can see that you can get the .Value property of XmlTextReader. But I
>> want
>> to be able to specify the node I want to look at.
>>
>> e.g.
>>
>> <Group>
>> <Items>
>> <Item>content here</Item>
>> <Item>some more content here</Item>
>> <Items>
>> <Activity></Activity>
>> <Location></Location>
>> </Group>
>>
>> thanks.
>>
>> CR[/color]
>
>[/color]

[CodeRazor]

Re: XmlTextReader - how find a particular node

Thanks for your help, but I am still stumped.

I have found an inelegant way of retrieving each item's title and
description using string methods. See my code below. I would like to know how
I can retrieve the <title> and <description> nodes more directly using the
methods of the XmlTextReader.

My xml file looks somthing like:
<items>
<item><title>Ti tle 1</title><descript ion>Description 1</description></item>
<item><title>Ti tle 2</title><descript ion>Description 2</description></item>
</items>

My Hack:
XmlTextReader xmlTextReader = new XmlTextReader(m yXmlUrl);

while(xmlTextRe ader.Read())
{
if(xmlTextReade r.NodeType == XmlNodeType.Ele ment && xmlTextReader.N ame ==
"item" )
{
string itemContent = xmlTextReader.R eadOuterXml();
int headlineStart = itemContent.Ind exOf("<title>") + "<title>".Lengt h;
headlineLength = itemContent.Ind exOf("</title>") - headlineStart;
descriptStart = itemContent.Ind exOf("<descript ion>") +
"<description>" .Length;
int descriptLength = itemContent.Ind exOf("</description>") - descriptStart;
string headline = itemContent.Sub string(headline Start,
headlineLength) ;
string description = itemContent.Sub string(descript Start, descriptLength) ;

Response.Write( headline + "<br>" + description + "<br><br>") ;
}

Many thanks,

CR