Assign and check for a null value at the same time?

Question

I have the following scenario:

if(xml.Descendants(ns + "Children").FirstOrDefault() != null)
{
    XElement children = xml.Descendants(ns + "Children").FirstOrDefault();
}

Is there a way I can check for null and assign the value at the same time instead of having to search for the value twice, something similar to:

//Not sure if this is correct.
if (XElement children = xml.Descendants(ns + "Children").FirstOrDefault() != null)
{

}

Answer 1

A variable assignment also returns the value. So the syntax in the form of the following will do:

SomeType someVariable;
if ((someVariable = valueToAssign) != null)
{
    // valueToAssign was not null
}

In your case:

XElement children;

if ((children = xml.Descendants(ns + "Children").FirstOrDefault()) != null)
{

}

Answer 2

I would do it this way:

XElement children = xml.Descendants(ns + "Children").FirstOrDefault();
if(children != null)
{
    //use children
}

Answer 3

You could just do

XElement children = xml.Descendants(ns + "Children").FirstOrDefault();

and then check for null

if (children != null) {...}