Linq查询where子句返回null

Question

This is the XML File I am trying to get the tag Element Posted_Status where Posted_Status has Ready

<?xml version="1.0" encoding="utf-8"?>
<Server>
      <Network> <---Network is the parent element
        <Posted_Status id="10">Ready</Posted_Status>
        <Timed_On id="10">7/28/2013 9:32:10 AM</Timed_On>
        <Timed_Off id="10">8/28/2013 9:32:10 AM</Timed_Off>
      </Network>
</Server>

I am having a problem where a linq query is returning null. I am trying to query an XML element. The element name is Posted_Status . The tag value is "Ready". I am trying to get the tag Posted_Status where the Posted_Status is equal to "Ready".

 // Query's the tag where the tag equals Ready
IEnumerable<XElement> expiration =
            from exp in main.Elements("Posted_Status")
            where (string)exp.Element("Posted_Status").Value == "Ready"
            select exp;

This execute or calls the query into action and display all the values from the Posted_Status XML tag where the tag value equals "Ready".

 foreach (string exp in expiration)
 {
     for (int i = 0; i < IntializedPostStat.Count(); i++)
     {
         IntializedPostStat[i] = exp.ToString();
         lstIntializations.Items.Add("[Posted_Status]......" 
             + IntializedPostStat[i].ToString());
         break;
     }
 }

Answer 1

You don't need to cast to string in where clause also you need to compare it against Value like

where exp.Element("Posted_Status").Value == "Ready"

Try:

var expiration =
       from exp in main.Elements("Network")
       where exp.Element("Posted_Status").Value.Equals("Ready", StringComparison.CurrentCulture)
       select
       new
       {
           Timed_On = exp.Element("Timed_On").Value,
           Timed_Off = exp.Element("Timed_Off").Value,
       };

For Ouput:

foreach (var item in expiration)
{
    Console.WriteLine("Timed_On: {0} \r\nTimed_Off: {1}", item.Timed_On, item.Timed_Off );
}

(Its better if you parse the values to a propert DateTime object)

Answer 2

Both your from and where read Element("Posted_Status") .

Edit based on updated question, this should be it:

XElement main = XDocument.Load(fi.FullName).Element("Server");
var expiration = from exp in main.Elements("Network")
 where exp.Element("Posted_Status").Value == "Ready"
 select exp;

You have to read the root element first. Then you iterate through all "Network" and check the "Posted_Status" value

This will return all "Network" elements that suit the condition