Expressing Designs in C# - Effective C# - page 133

#region IEnumerable Members
System.Collections. IEnumerator
System.Collections. IEnumerable .GetEnumerator()
{
return getElements();
}
#endregion
}
The WeatherStream class models a sequence of weather observations. To do
that it implements IEnumerable<WeatherData>. That means creating two
methods: the GetEnumerator<T> method and the classic GetEnumerator
method. The latter interface is explicitly implemented so that client code
would naturally be drawn to the generic interface over the version typed
as System.Object.
Implementing those two methods means that the WeatherStream class
supports all the extension methods defined in System.Linq.Enumerable.
That means WeatherStream can be a source for LINQ queries:
var warmDays = from item in
new WeatherDataStream ( "Ann Arbor" )
where item.Temperature > 80
select item;
LINQ query syntax compiles to method calls. The query above translates
to the following calls:
var warmDays2 = new WeatherDataStream ( "Ann Arbor" ).
Where(item => item.Temperature > 80 ).
Select(item => item);
In the code above, the Where and Select calls look like they belong to
IEnumerable<WeatherData>. They do not. Those methods appear to
belong to IEnumerable<WeatherData> because they are extension meth-
ods. They are actually static methods in System.Linq.Enumerable. The
compiler translates those calls into the following static calls:
// Don't write this, for explanatory purposes
var warmDays3 = Enumerable .Select(
Enumerable .Where(
new WeatherDataStream ( "Ann Arbor" ),
item => item.Temperature > 80 ),
item => item);