XElement NullReferenceException

I have the following code.

 XElement opCoOptOff = doc.Descendants(ns + "OpCoOptOff").FirstOrDefault();
 String opCo = opCoOpt开发者_如何学PythonOff.Element(ns + "strOpCo").Value;

Now if the element I return is null, I am getting a NullReferenceException since the XElement is null. So I changed it to the following.

String opCo = opCoOptOff.Element(ns + "strOpCo").Value;
 if(opCoOptOff != null)
        {
String opCo = opCoOptOff.Element(ns + "strOpCo").Value;

I am hoping there has to be a more elegant way to do this since this scenario comes up often and I would like to avoid doing this type of check every time there is an issue. Any assistance would be greatly appreciated

You can write an extension method and use it anywhere:

public static class XDocumentExtension
{
   public static string GetSubElementValue(this XElement element, string item)
   {
        if(element != null && element.Value != null)
        {
           if (element.Element(item) != null)
           {
              return element.Element(item).Value;
           }
        }
        return null;
   }

   public static XElement GetElement(this XElement element, string item)
   {
        if (element != null)
            return element.Element(item);

        return null;
   }

   public static XElement GetElement(this XDocument document, string item)
   {
        if (document != null)
           return document.Descendants("item").FirstOrDefault();
        return null;
   }
}

Use it as :

String opCo = opCoOptOff.Element(ns + "strOpCo").GetSubElementValue(ns + "strOpCo");

Also you can add other extensions for your purpose.

Edit: I'd updated answer but if you read it carefully before I wrote you can add other extensions for your purpose. I wrote this because I guess you may be want to call on null objects Element, I don't know what's exact situation of yours but I add some code for more clarification, depend on your situation complete the XDocumentExtension class, and one note extension methods can work on null objects.

You can actually cast the XElement directly to a string: http://msdn.microsoft.com/en-us/library/bb155263.aspx

so

String opCo = opCoOptOff.Element(ns + "strOpCo").Value;

could be

string opCo = (string) opCoOptOff.Element(ns + "strOpCo");