Linq to XML - Check if Element exists

Question

User1409124252 posted

I have seen some other solutions to this, but they don't fit what I am trying to do.  The XML has elements that may not be in the file each time it is posted.

The trick is, the query is dependent upon a question value to get the answer value.  Here is the code:

            string otherphone = (from e in contact.Descendants("DataElement")
                                where e.Element("QuestionName").Value == "other_phone"
                                select (string)e.Element("Answer").Value).FirstOrDefault();
            otherphone = (!String.IsNullOrEmpty(otherphone)) ? otherphone.Replace("'", "''") : null;

Under the "contact" collection, here are many elements named "DataElement", so I am querying to find the one where the elements QuestionName is "other_phone", then I get the Answer value.

How can I make it work if this element doesn't exist in the file?

Answer 1

User1918509225 posted

Hi indyitman,

For your post ,here are my suggestion:

First ,get all the elements  whose name is DataElement,just like below:

IEnumerable<XElement> q = from ele in ex.Elements("DataElement")
                           Select ele;

Seconde iterate the elements founded above,and find if its chid element has a  element named “QuestionName”,

if it has,get the value,if not have ,just skip the loop,just like code below:

            string val="";
            foreach (XElement x in q.Elements()) {
               
                if (x.Name == "QuestionName") {
                    val = x.Value;
                }

            }

If you have more than one element “QuestionName”,you can try to add the value into a List<string>,just like below:

 List<string> list=new List<string>();
 foreach (XElement x in q.Elements()) {
               
                if (x.Name == "QuestionName") {
                    list.Add(x.Value);
                }

            }

Hope it can help you.

Answer 2

User1409124252 posted

Thanks very much Kevin, but I found the answer was simply changing null to "".

string otherphone = (from e in contact.Descendants("DataElement")
                                where e.Element("QuestionName").Value == "other_phone"
                                select (string)e.Element("Answer").Value).FirstOrDefault();
            otherphone = (!String.IsNullOrEmpty(otherphone)) ? otherphone.Replace("'", "''") : "";