Accessing a property then a method

Question

Hi

Ive seen it time and time again whereby an instance property member of a class is accessed followed by an instance method, all of the same line.

For example given this source code:-

var doc = XDocument.Load("aUrlReferencingaXMLDoc");

foreach(var item in doc.Root.Elements())

What I would like to know is how is this possible to access the Elements method straight from the Root property? is is because they both have the same Return type, in this case XElement?

Regards

Steven

Vulpes · Answer

That's right. If a property returns an object of a certain type and that object has a method (or inherits a method from its base class) which you want to call then you can chain the two operations together as in the above line. In fact you can continue with this chaining (unless it's a void method) but if you carry this too far then the point will be reached where the code becomes difficult to read and hence maintain.

S · Answer

Brilliant thank you Vulpes!

S · Answer

Thanks Vulpes. In general being able to access various instance members using the notation property then method as like the example below:- doc.Root.Elements(); Depends on the Return type of the object and also class inheritance ie Root could be of type XElement and Elements say for arguement sake could be of type XNode? being able to use the 2 side by side is due to the fact XNode inherits from XElement? Regards Steven

Vulpes · Answer

Well doc.Root returns an XElement (namely the root element of the document) and when you the call its Elements() method it returns all its child elements as an IEnumerable . You can then enumerate the individual XElements in this IEnumerable using foreach. LINQ to XML methods usually return a collection as an IEnumerable rather than an array or list of XElements so that the collection is not actually created until it's enumerated. This 'deferred (or lazy) execution' decouples query creation from execution which has certain technical advantages.

S · Answer

That said when browsing other instance methods of the XDocument class not all of them have the same Return type XElement which implies that class inheritance is in play?