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Read Xml with Descendants Method (XName)

, 19 Nov 2012
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This post is about understanding Descendants and avoid misconception with this method.Recently I read one question on StackOverFlow  about reading xml using Linq To Xml to get node values. In that developer made use of Descendants Method to get the child node values.Let see the actual problem here


This post is about understanding Descendants and avoid misconception with this method.
Recently I read one question on StackOverFlow about reading XML using LINQ To XML to get node values. In that developer made use of Descendants Method to get the child node values.

Let see the actual problem here following is XML to read. And developer wrote code to read out value of orderid node.
<ordersreport date="2012-08-01">
<returns>
      <amount>
        <orderid>2</orderid>
        <orderid>3</orderid>
        <orderid>21</orderid>
        <orderid>23</orderid>
      </amount>
    </returns>
</ordersreport>
So code written like this
    var amount = documentRoot.Descendants("Amount")
               .Select(y => new
               {
                  OrderId = (int)y.Element("OrderId")
               });
               foreach (var r in amount)
               {
                  Console.WriteLine(r.OrderId);
               }
Ouput of above code is
 2
that is only first orderid element value which is child of Amount , So misconception here by developer of the code is Descendants("Amount") returns child element of the Amount tag i.e. all orderId element.

Now to Understand Descendants  function in better way I visited to MSDN link which says something like this
XContainer.Descendants Method (XName) - Returns a filtered collection of the descendant elements for this document or element, in document order. Only elements that have a matching XName are included in the collection. So as per the definition on MSDN problem with code
    var amount = doc.Descendants("Amount")                         
      .Select(y => new
      {
       OrderId = (int)y.Element("OrderId")
       });
will give you Element Amount and when you write y.Element("OrderId") will return you fist element of its child.
Descendants - doesn't mean than its return the child element of element name rather than method look for descendants of element or if name of element specified as parameter than matching descendants.
Finally I got following solution to get it properly work
XElement documentRoot  = 
     XElement.Parse (@"<ordersreport date="2012-08-01">
                             <returns>
                              <amount>
                                  <orderid>2</orderid>                                                    
                                  <orderid>3</orderid>
                                  <orderid>21</orderid>
                                  <orderid>23</orderid>
                               </amount>
                             </returns>
                        </ordersreport>");
Solution 1
var orderids = from order in
                  documentRoot.Descendants("Amount").Descendants()
                  select new
                  {
                     OrderId = order.Value
                  };
As per the information on MSDN documentRoot.Descendants("Amount").Descendants() give list of orderId elements.

Solution 2
var orderids = from order in
                    documentRoot.Descendants("OrderId")
                    select new
                    {
                       OrderId = order.Value
                    };
or the second solution is just bit easy than this just make use of documentRoot.Descendants("OrderId") that will give all orderid element.
Conclusion
This post is just for avoiding misconception related to Descendants and understand it properly.

Leave your comments if you like it.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Pranay Rana
Software Developer (Senior) GMind Solusion
India India

Microsoft C# MVP (12-13)

 
Hey, I am Pranay Rana, working as a ITA in MNC. Web development in Asp.Net with C# and MS sql server are the experience tools that I have had for the past 5.5 years now.
 
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