CODEWITHSUNDEEP
xmlwindowslinqwindows-phone-7
lookitskris
lookitskris

Reputation: 678

Loading data from XML Document throwing a NullReferenceException when using XDocument on Windows Phone 7

Ok. So with a Windows Phone 7 app, say I have the following XML file

<Objects>
    <Object Property1=”Value1” Property2=”Value2”>
        <Property3>Value3</Property3>
    </Object>
    <Object Property1=”Value1” Property2=”Value2”>
        <Property3>Value3</Property3>
    </Object>
</Objects>

And I have the following class definition

public class myObject
{
    public string Property1 { get; set; }
    public string Property2 { get; set; }
    public string Property3 { get; set; }

    public myObject (string _property1, string _property2, string _property3)
    {
        this.Property1 = _property1
        this.Property1 = _property1
        this.Property1 = _property1
    }
}

and I then use the following code to load the data from the XML file and return a list of myObjects:-

var xdoc = XDocument.Load("myXMLFile.xml");
var result = from o in xdoc.Document.Descendants("Object")
                         select new myObject
                         {
                             Property1 = o.Element("Property1").Value,
                             Property2 = o.Element("Property2").Value,
                             Property3 = o.Element("Property3").Value,
                         };

return result.ToList<myObject>();

Why is this returning a NullReferenceException? I'm guessing it is my linq query not being quite right as the file is being loaded just fine with the XDocument.Load call.

any help would be fantastic!

Kris

Upvotes: 1

Views: 1407

Answers (2)

Steven K.
Steven K.

Reputation: 2106

For the xml structure as you present it, you will need a linq query like this:

var xdoc = XDocument.Load("myXMLFile.xml");
var result = from o in xdoc.Document.Descendants("Object")
     select new myObject
     {
         Property1 = o.Attribute("Property1").Value,
         Property2 = o.Attribute("Property2").Value,
         Property3 = o.Element("Property3").Value
     };

Like John said, o.Attribute("attributeName") or o.Element("elementName") will throw a NullReferenceException when the element or attribute don't exist.

Upvotes: 4

John Saunders
John Saunders

Reputation: 161791

Property1 = o.Element("Property1").Value

will throw a NullReferenceException when run against an "o" that does not have a "Property1" element! The Element method will return null.

Upvotes: 0

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