XElement.Element doesn't return a null value-CodePudding

When I run the program and I set a wrong value for _moduleParent the exception appears and says 'Object reference not set to an instance of an object.'

I want to return a null string. How can I deal with this exception?

string sioModuleName = "";
string sioModuleDescription = String.Empty;
try
{
    XDocument xDoc = new XDocument();
    xDoc = XDocument.Load(_xmlPath);
    //Root
    var sioModule = xDoc.Element(_moduleName);
    if(sioModule != null)
    {
        sioModuleName = sioModule.Element(_moduleParent).Value;//here is the problem
        sioModuleDescription = sioModule.Element("SIO-DEFINITION").Value;
    }
    else
    {
        MessageBox.Show("Incorrect Module Name");
        return;
    }
}

CodePudding user response：

XContainer.Element(XName) returns an XElement if an element with the specified name exists, otherwise it will return null. Your exception occurs because you are reading the Value property of a null reference. So you need to handle that. There are two options:

Use the built-in explicit conversions:

sioModuleName = (string)sioModule.Element(_moduleParent);

Use the null-conditional operator:

sioModuleName = sioModule.Element(_moduleParent)?.Value;