Question

I am just trying to read some details from an XML file, part of which looks like this:

<appender name="FILE" class="applications.core.logging.CustomFileAppender">
    <param name="File" value="C:\\Logs\\File.log"/>
    <param name="MaxBackupIndex" value="5"/>
</appender>
<appender name="FILE" class="applications.core.logging.CustomFileAppender">
    <param name="File" value="C:\\Logs\\File2.log"/>
    <param name="MaxBackupIndex" value="17"/>
</appender>
<appender name="FILE" class="applications.core.logging.CustomFileAppender">
    <param name="File" value="C:\\Logs\\File3.log"/>
    <param name="MaxBackupIndex" value="98"/>
</appender>

I have several of these ‘appender’ nodes in my XML file. The following code loops through each ‘appender’ node. Within each ‘appender’ I want to pick out the param node with name “File” and check if the value is equal to what I am looking for.

foreach (XElement node in XmlFile.Descendants("appender"))
        {
            IEnumerable<XElement> elements = from el in node.Elements("param") 
                                             where el.Attribute("value").ToString().Equals("C:\\Logs\\File.log")) 
                                             select el;

            foreach (XElement el in elements)
            {
                Console.WriteLine("Found it " + el.Name);
                // Now read value for MaxBackupIndex
            }
        }

However my code is not printing anything out, so I think possibly the ‘where’ part of my LINQ query is incorrect, can anybody spot where I am going wrong?

Answer 1

You’re calling XAttribute.ToString(). Try using XAttribute.Value instead, or just cast to a string. ToString() will return value="C:\\Logs\\File.log" – the name and the value – whereas you just want the value:

var elements = from el in node.Elements("param")
               where (string) el.Attribute("value") == "C:\\Logs\\File.log"
               select el;

Personally I wouldn’t bother with a query expression here, btw:

var elements = node.Elements("param")
         .Where(el => (string) el.Attribute("value") == "C:\\Logs\\File.log")

EDIT: Additionally, as others have said, you want to have single backslashes in the XML file.