Using XmlDocument to Retrieve values in c#

Question

I am using XmlDocument() for parsing a file like **.opf ** for my application of EpubReader.

<item id="W01MB154" href="01MB154.html" media-type="application/xhtml+xml" />
<item id="W000Title" href="000Title.html" media-type="application/xhtml+xml" />

with

  <itemref idref="W000Title" />
  <itemref idref="W01MB154" />

These values in same file.

Here I know the value of id within the tag of item, after that I want to know the value of the href element.

What I have to do is compare the value idref element in the itemref tag with element value of id in the tag item. Here I know the id value which is W01MB154.

Simply, I want to know the next value of id which is href element, Using XmlDocument().

Answer 1

Following code loads and parses content.opf file without any error.

To iterate and compare above xml you may use following code:

try
{
    XmlDocument xDoc = new XmlDocument();
    xDoc.Load("content.opf");

    XmlNodeList items = xDoc.GetElementsByTagName("item");
    foreach (XmlNode xItem in items)
    {
        string id = xItem.Attributes["id"].Value;
        string href= xItem.Attributes["href"].Value;
    }
}
catch (Exception ex)
{
    System.Diagnostics.Debug.WriteLine(ex.Message);
}

Answer 2

You may start with the following code. When I execute it, I get proper output:

string str = @"<?xml version='1.0' encoding='UTF-8'?><root><items><item id='W01MB154' href='01MB154.html' media-type='application/xhtml+xml' /><item id='W000Title' href='000Title.html' media-type='application/xhtml+xml' /></items><itemrefs><itemref idref='W000Title' /><itemref idref='W01MB154' /></itemrefs></root>";
XmlDocument xml = new XmlDocument();
xml.LoadXml(str);  // suppose that str string contains the XML data. You may load XML data from a file too.

XmlNodeList itemRefList = xml.GetElementsByTagName("itemref");
foreach (XmlNode xn in itemRefList)
{
    XmlNodeList itemList = xml.SelectNodes("//root/items/item[@id='" + xn.Attributes["idref"].Value + "']");
    Console.WriteLine(itemList[0].Attributes["href"].Value);
}

Output:

000Title.html

01MB154.html

The XML used is:

<?xml version='1.0' encoding='UTF-8'?>
<root>
    <items>
        <item id='W01MB154' href='01MB154.html' media-type='application/xhtml+xml' />
        <item id='W000Title' href='000Title.html' media-type='application/xhtml+xml' />
    </items>
    <itemrefs>
        <itemref idref='W000Title' />
        <itemref idref='W01MB154' />
    </itemrefs>
</root>

Check the structure of the XML document and the XPath expression.