var List1 = (IEnumerable<XElement>)null;
var List2 = (IEnumerable<XElement>)null;
var List3 = (IEnumerable<XElement>)null;
var List4 = (IEnumerable<XElement>)null;
var List1 = default(null);
var List2 = default(null);
var List3 = default(null);
var List4 = default(null);
var List1 = (string)null;
var List2 = (string)null;
var List3 = (string)null;
var List4 = (string)null;
var List1 = (string)null;
var List2 = (string)null;
var List3 = (string)null;
var List4 = (string)null;
We can define var as null , with typecasting when we already know the type of object which we want to store further in our code, or when we are not sure of the object we want to store we can use default(null) to define the that variable.
XmlNodeList List2 = default(XmlNodeList);
XmlNodeList List3 = default(XmlNodeList);
XmlNodeList List4 = default(XmlNodeList);
XmlNodeList List5 = default(XmlNodeList);
