Reading XML using XDocument & Linq - check if element is NULL?

Question

I'm using LINQ together with XDocument to read a XML File. This is the code:

XDocument xml = XDocument.Load(filename);

var q = from b in xml.Descendants("product")
        select new
        {
            name = b.Element("name").Value,
            price = b.Element("price").Value,                    
            extra = b.Element("extra1").Value,
            deeplink = b.Element("deepLink").Value                   
        };

Now the problem is, the extra1 field is not always present. There are items in the XML file without that node. If that happens it's crashing with a NullReferenceException.

Is there any possibility to include a "check if null" so I can prevent it from crashing?

dtb · Accepted Answer · 2010-04-07 17:48:31Z

43

Use (string) instead of .Value:

var q = from b in xml.Descendants("product")
        select new
        {
            name = (string)b.Element("name"),
            price = (double?)b.Element("price"),                    
            extra = (string)b.Element("extra1"),
            deeplink = (string)b.Element("deepLink")                   
        };

This also works with other datatypes, including many nullable types in case the element is not always present.

edited Apr 7, 2010 at 17:48

answered Apr 7, 2010 at 17:36

dtb

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Comments

MarekBaron · Accepted Answer · 2010-04-12 06:12:05Z

9

You can use "null coalescing" operator:

var q = from b in xml.Descendants("product")
        select new
        {
            name = (string)b.Element("name") ?? "Default Name",
            price = (double?)b.Element("price") ?? 0.0,                    
            extra = (string)b.Element("extra1") ?? String.Empty,
            deeplink = (string)b.Element("deepLink") ?? String.Empty                   
        };

This way, you will have full control about default value used when there's no element.

edited Apr 12, 2010 at 6:12

answered Apr 8, 2010 at 6:08

MarekBaron

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1 Comment

AakashM Over a year ago

price needs to be double? for that line to make sense.

Bart Verkoeijen · Accepted Answer · 2012-09-25 01:38:59Z

2

Use the following example for checking existence of any element before using that element.

if( b.Elements("extra1").Any() )
{
   extra = b.Element("extra1").Value;
}

edited Sep 25, 2012 at 1:38

Bart Verkoeijen

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answered Sep 11, 2012 at 12:47

Ashok Kumar

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Comments

Bill the Lizard · Accepted Answer · 2012-07-27 11:45:08Z

1

Here is sample example to read XML file using XDocument.

  XDocument objBooksXML = XDocument.Load(Server.MapPath("books.xml"));
    var objBooks = from book in
                   objBooksXML.Descendants("Book")
                   select new { 
                                Title = book.Element("Title").Value, 
                                Pages = book.Element("Pages").Value 
                              };

    Response.Write(String.Format("Total {0} books.", objBooks.Count()));
    gvBooks.DataSource = objBooks;
    gvBooks.DataBind();

edited Jul 27, 2012 at 11:45

Bill the Lizard

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answered Jul 6, 2012 at 10:10

Jayesh Sorathia

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1 Comment

Bil Simser Over a year ago

The problem with this code is that if "Book" doesn't contain a "Title" or "Pages" element you'll throw a null exception when trying to get .Value from either of them.

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