IEnumerable - why does this code work?
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So basically the code below just creates an XML document in memory and then parses it and spits the values back out. The question I have is about the IEnumerable statements. I never implemented a class that uses the interface, but yet it still works in this code. Does the compiler automagically create a container or something? How does this work? Does this work for all interfaces?
class Program
{
static void Main(string[] args)
{
XDocument employeeDoc =
new XDocument(
new XElement("Employees",
new XElement("Employee",
new XElement("Name" , "Bob Smith"),
new XElement("Phone" , "408-555-1000"),
new XElement("Phone" , "408-555-1001")),
new XElement("Employee",
new XElement("Name", "Sally Jones"),
new XElement("Phone", "415-555-2000"),
new XElement("Phone", "415-555-2001"))
)
);XElement root = employeeDoc.Element("Employees"); IEnumerable employees = root.Elements(); foreach (XElement emp in employees) { XElement empNameNode = emp.Element("Name"); Console.WriteLine(empNameNode.Value); IEnumerable empPhones = emp.Elements("Phone"); foreach (XElement phone in empPhones) { Console.WriteLine(" {0}", phone.Value); } } }}
Have a look at the definition of the
XContainer.Elementsmethod[^]. The type that this returns is anIEnumberablecollection. This allows you to run a loop over the elements of theemployeesobject you create. It actually has nothing to do with you implementing or not implementing the interface, since the classXContainer/XElementpossibly itself takes care of this internally. -
Karthik, I'm still a little confused. I know that the foreach statement requires a type that has implemented the IEnumerable or IEnumerator interface, what I don't understand is why the line
IEnumerable employees = root.Elements()even works. I didn't implement the IEnumerable interface in a class anywhere. I just used that statement. In the book I'm reading it says that interfaces have to be a part of the classes declaration, for instance:public class Myclass : IEnumerableSince I didn't do that, does the compiler make an object with the proper code for me, from the first code example?The XElement.Elements Method Returns a collection of the child elements of this element or document, in document order. as given here. http://msdn.microsoft.com/en-us/library/system.xml.linq.xelement.elements.aspx[^]. This collection implements IEnumerable, hence you could write the statement
IEnumerable employees = root.Elements(); -
Have a look at the definition of the
XContainer.Elementsmethod[^]. The type that this returns is anIEnumberablecollection. This allows you to run a loop over the elements of theemployeesobject you create. It actually has nothing to do with you implementing or not implementing the interface, since the classXContainer/XElementpossibly itself takes care of this internally. -
Have a look at the definition of the
XContainer.Elementsmethod[^]. The type that this returns is anIEnumberablecollection. This allows you to run a loop over the elements of theemployeesobject you create. It actually has nothing to do with you implementing or not implementing the interface, since the classXContainer/XElementpossibly itself takes care of this internally. -
The XElement.Elements Method Returns a collection of the child elements of this element or document, in document order. as given here. http://msdn.microsoft.com/en-us/library/system.xml.linq.xelement.elements.aspx[^]. This collection implements IEnumerable, hence you could write the statement
IEnumerable employees = root.Elements(); -
The XElement.Elements Method Returns a collection of the child elements of this element or document, in document order. as given here. http://msdn.microsoft.com/en-us/library/system.xml.linq.xelement.elements.aspx[^]. This collection implements IEnumerable, hence you could write the statement
IEnumerable employees = root.Elements(); -
The XElement.Elements Method Returns a collection of the child elements of this element or document, in document order. as given here. http://msdn.microsoft.com/en-us/library/system.xml.linq.xelement.elements.aspx[^]. This collection implements IEnumerable, hence you could write the statement
IEnumerable employees = root.Elements();5+
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