Linq To Xml Null Checking of attributes

Answer 1

In C# 6.0 you can use monadic Null-conditional operator ?. After applying it in your example it would look like this:

var books = from book in booksXml.Descendants("book")
            select new
            {
                Name = book.Attribute("name")?.Value ?? String.Empty,
                Price = Convert.ToInt32(book.Attribute("price")?.Value ?? "0"),
                Special = book.Attribute("special")?.Value ?? String.Empty
            };

You can read more here in part titled Null-conditional operators.

Answer 2

How about using an extension method to encapsulate the missing attribute cases:

public static class XmlExtensions
{
    public static T AttributeValueOrDefault<T>(this XElement element, string attributeName, T defaultValue)
    {
        var attribute = element.Attribute(attributeName);
        if (attribute != null && attribute.Value != null)
        {
            return (T)Convert.ChangeType(attribute.Value, typeof(T));
        }

        return defaultValue;
    }
}

Note that this will only work if T is a type to which string knows to convert via IConvertible. If you wanted to support more general conversion cases, you may need to look for a TypeConverter, as well. This will throw an exception if the type fails to convert. If you want those cases to return the default as well, you'll need to perform additional error handling.

Answer 3

You can cast the attribute to a string. If it is absent you will get null and subsequent code should check for null, otherwise it will return the value directly.

Try this instead:

var books = from book in booksXml.Descendants("book")
            select new
            {
                Name = (string)book.Attribute("name"),
                Price = (string)book.Attribute("price"),
                Special = (string)book.Attribute("special")
            };