Question

I have xml code that would be something like this:
file named: player.xml

<root>
  <person>
    <fname>Dwight</fname>
    <lname>Howard</lname>
    <vertLeap>
      <try1>32.33</try1>
      <try2>33.33</try2>
      <try3>34.33</try3> 
    </vertLeap>
  </person>
  <person>
    <fname></fname>
    <lname>Jordan</lname>
    <vertLeap>
      <try1>40.33</try1> 
    </vertLeap>
  </person>
</root>

This isn’t my real xml, but should work for the example.
Now I want to use linq to xml to read the data. Iam am trying like this.

Class:

public class Player
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int Leap1 { get; set; }
    public int Leap2 { get; set; }
    public int Leap3 { get; set; }

    public WritePlayertoDatabase()
    {
        //do stuff to write
    }
}

Query:

XDocument xDoc = XDocument.Load("player.xml");
var player_query = from p xDoc.Desendants("person")
                   select new Player
                   {
                       FirstName = p.Element("fname"),
                       LastName = p.Element("lname"),
                       Leap1 = p.Element("try1"),
                       Leap2 = p.Element("try2"),
                       Leap3 = p.Element("try3")
                   };

I’m getting a NullReferenceException. Is there a way to test if the elements exist before I try to use the value? Or is there a way better way to accomplish this?

Answer 1

So there are a few things wrong with your linq query.

1) p.Element("fname") will return the fname XML Element, not a string. So you still need to get the element’s value. Similarly, the Leap1-3 properties are int, but you will get the element value as a stirng and need to convert it. But, try1-3 are not ints in the xml, so you probably want to change the type to somehting else in the Player class.

2) try1 – tryx element s are all children of ‘vertleap’. You can’t directly get element ‘try1’ from ‘person’. It will be null.

So how about something more like this:

    var player_query = from p in xDoc.Descendants("person")
                       select new Player
                       {
                           FirstName =  p.Element("fname") != null ? p.Element("fname").Value : "",
                           LastName = p.Element("lname") != null ? p.Element("lname").Value : "",
                           Leap1 = p.Element("vertLeap") != null ? (p.Element("vertLeap").Element("try1") != null ? Decimal.Parse(p.Element("vertLeap").Element("try1").Value) : 0) : 0,

                           Leap2 = p.Element("vertLeap") != null ? (p.Element("vertLeap").Element("try2") != null ? Decimal.Parse(p.Element("vertLeap").Element("try2").Value) : 0) : 0,
                           Leap3 = p.Element("vertLeap") != null ? (p.Element("vertLeap").Element("try3") != null ? Decimal.Parse(p.Element("vertLeap").Element("try3").Value) : 0) : 0,
                       };