C# Checking elements in xml file

Question

I have the below xml file:

  <Resources>
    <a>123.png</a>
 </Resources>
 <Resources>
    <a>Background\345.png</a>
 </Resources>
<Resources>
    <b>d1.wav</b>
</Resources>

I want to check for the elements to do different function:

        foreach (var downloadFile in downloadFiles.Elements("Resources"))
        {
            if (downloadFile.Element("a").Value != null)
            {
                  // function for a
            }
            else if (downloadFile.Element("b").Value != null)
            {
                  // function for b
            }
         }

There will be error " System.NullReferenceException " when the loop reach element b.

Do you guys know what's wrong?

Answer 1

Looking at your XML, not all resources have the b element, so you get NRE because Element("b") returns null. If you want to check whether the element exists compare the Element to null without accessing Value property:

if (downloadFile.Element("b") != null)